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	$146.81	4.788%	$153.8393	$153.84	$153.85	$153.80
Purchase #2	$22.88	8.812%	$24.8962	$24.90	$24.90	$24.90
Purchase #3	$100.46	8.434%	$108.9328	$108.93	$108.95	$108.90
Purchase #4	$59.43	13.281%	$67.3229	$67.32	$67.30	$67.30
Purchase #5	$28.47	13.509%	$32.316	$32.32	$32.30	$32.30
Purchase #6	$170.27	5.505%	$179.6434	$179.64	$179.65	$179.60
Purchase #7	$5.85	9.290%	$6.3935	$6.39	$6.40	$6.40
7 purchase totals =	$534.17		$573.3441	$573.34	$573.35	$573.20