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	$191.96	6.256%	$203.969	$203.97	$203.95	$204.00
Purchase #2	$37.27	11.865%	$41.6921	$41.69	$41.70	$41.70
Purchase #3	$19.98	10.645%	$22.1069	$22.11	$22.10	$22.10
Purchase #4	$88.94	11.551%	$99.2135	$99.21	$99.20	$99.20
Purchase #5	$62.72	4.603%	$65.607	$65.61	$65.60	$65.60
Purchase #6	$19.54	11.142%	$21.7171	$21.72	$21.70	$21.70
Purchase #7	$38.54	5.490%	$40.6558	$40.66	$40.65	$40.70
7 purchase totals =	$458.95		$494.9614	$494.97	$494.90	$495.00