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	$82.56	13.677%	$93.8517	$93.85	$93.85	$93.90
Purchase #2	$64.94	9.853%	$71.3385	$71.34	$71.35	$71.30
Purchase #3	$80.69	11.794%	$90.2066	$90.21	$90.20	$90.20
Purchase #4	$14.65	8.325%	$15.8696	$15.87	$15.85	$15.90
Purchase #5	$5.30	6.513%	$5.6452	$5.65	$5.65	$5.60
Purchase #6	$249.57	10.316%	$275.3156	$275.32	$275.30	$275.30
Purchase #7	$86.37	4.363%	$90.1383	$90.14	$90.15	$90.10
7 purchase totals =	$584.08		$642.3655	$642.38	$642.35	$642.30