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	$146.26	5.366%	$154.1083	$154.11	$154.10	$154.10
Purchase #2	$128.59	9.835%	$141.2368	$141.24	$141.25	$141.20
Purchase #3	$83.39	7.526%	$89.6659	$89.67	$89.65	$89.70
Purchase #4	$92.58	10.562%	$102.3583	$102.36	$102.35	$102.40
Purchase #5	$106.42	11.375%	$118.5253	$118.53	$118.55	$118.50
Purchase #6	$133.81	13.226%	$151.5077	$151.51	$151.50	$151.50
Purchase #7	$137.59	11.472%	$153.3743	$153.37	$153.35	$153.40
7 purchase totals =	$828.64		$910.7766	$910.79	$910.75	$910.80