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	$220.54	11.434%	$245.7565	$245.76	$245.75	$245.80
Purchase #2	$36.65	5.444%	$38.6452	$38.65	$38.65	$38.60
Purchase #3	$32.32	3.343%	$33.4005	$33.40	$33.40	$33.40
Purchase #4	$85.73	4.203%	$89.3332	$89.33	$89.35	$89.30
Purchase #5	$221.74	8.560%	$240.7209	$240.72	$240.70	$240.70
Purchase #6	$83.52	8.740%	$90.8196	$90.82	$90.80	$90.80
Purchase #7	$137.31	10.177%	$151.284	$151.28	$151.30	$151.30
7 purchase totals =	$817.81		$889.9599	$889.96	$889.95	$889.90