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	$170.28	4.755%	$178.3768	$178.38	$178.40	$178.40
Purchase #2	$139.82	10.172%	$154.0425	$154.04	$154.05	$154.00
Purchase #3	$213.30	10.104%	$234.8518	$234.85	$234.85	$234.90
Purchase #4	$147.96	12.216%	$166.0348	$166.03	$166.05	$166.00
Purchase #5	$200.76	7.841%	$216.5016	$216.50	$216.50	$216.50
Purchase #6	$146.33	3.408%	$151.3169	$151.32	$151.30	$151.30
Purchase #7	$78.81	8.523%	$85.527	$85.53	$85.55	$85.50
7 purchase totals =	$1,097.26		$1,186.6514	$1,186.65	$1,186.70	$1,186.60