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	$160.35	7.113%	$171.7557	$171.76	$171.75	$171.80
Purchase #2	$90.34	6.114%	$95.8634	$95.86	$95.85	$95.90
Purchase #3	$89.59	11.300%	$99.7137	$99.71	$99.70	$99.70
Purchase #4	$223.97	10.495%	$247.4757	$247.48	$247.50	$247.50
Purchase #5	$142.55	3.209%	$147.1244	$147.12	$147.10	$147.10
Purchase #6	$42.49	3.773%	$44.0931	$44.09	$44.10	$44.10
Purchase #7	$85.64	3.116%	$88.3085	$88.31	$88.30	$88.30
7 purchase totals =	$834.93		$894.3345	$894.33	$894.30	$894.40