Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.36	12.516%	$151.1765	$151.18	$151.20	$151.20
Purchase #2	$166.62	11.121%	$185.1498	$185.15	$185.15	$185.10
Purchase #3	$165.92	7.611%	$178.5482	$178.55	$178.55	$178.50
Purchase #4	$130.98	10.290%	$144.4578	$144.46	$144.45	$144.50
Purchase #5	$229.79	10.653%	$254.2695	$254.27	$254.25	$254.30
Purchase #6	$129.80	11.324%	$144.4986	$144.50	$144.50	$144.50
Purchase #7	$240.42	7.221%	$257.7807	$257.78	$257.80	$257.80
7 purchase totals =	$1,197.89		$1,315.8811	$1,315.89	$1,315.90	$1,315.90