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	$133.58	10.705%	$147.8797	$147.88	$147.90	$147.90
Purchase #2	$16.96	9.433%	$18.5598	$18.56	$18.55	$18.60
Purchase #3	$15.25	4.146%	$15.8823	$15.88	$15.90	$15.90
Purchase #4	$39.70	13.224%	$44.9499	$44.95	$44.95	$44.90
Purchase #5	$192.56	3.457%	$199.2168	$199.22	$199.20	$199.20
Purchase #6	$137.76	13.494%	$156.3493	$156.35	$156.35	$156.30
Purchase #7	$31.50	3.306%	$32.5414	$32.54	$32.55	$32.50
7 purchase totals =	$567.31		$615.3792	$615.38	$615.40	$615.30