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	$53.72	11.285%	$59.7823	$59.78	$59.80	$59.80
Purchase #2	$131.86	6.519%	$140.456	$140.46	$140.45	$140.50
Purchase #3	$250.45	7.607%	$269.5017	$269.50	$269.50	$269.50
Purchase #4	$202.38	11.203%	$225.0526	$225.05	$225.05	$225.10
Purchase #5	$224.97	6.118%	$238.7337	$238.73	$238.75	$238.70
Purchase #6	$159.26	8.757%	$173.2064	$173.21	$173.20	$173.20
Purchase #7	$41.52	7.240%	$44.526	$44.53	$44.55	$44.50
7 purchase totals =	$1,064.16		$1,151.2587	$1,151.26	$1,151.30	$1,151.30