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	$141.79	4.285%	$147.8657	$147.87	$147.85	$147.90
Purchase #2	$199.27	7.557%	$214.3288	$214.33	$214.35	$214.30
Purchase #3	$26.58	6.485%	$28.3037	$28.30	$28.30	$28.30
Purchase #4	$210.58	13.144%	$238.2586	$238.26	$238.25	$238.30
Purchase #5	$67.45	7.740%	$72.6706	$72.67	$72.65	$72.70
Purchase #6	$52.39	8.611%	$56.9013	$56.90	$56.90	$56.90
Purchase #7	$36.43	10.786%	$40.3593	$40.36	$40.35	$40.40
7 purchase totals =	$734.49		$798.6880	$798.69	$798.65	$798.80