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	$8.30	7.575%	$8.9287	$8.93	$8.95	$8.90
Purchase #2	$149.89	8.426%	$162.5197	$162.52	$162.50	$162.50
Purchase #3	$78.55	10.225%	$86.5817	$86.58	$86.60	$86.60
Purchase #4	$106.62	4.359%	$111.2676	$111.27	$111.25	$111.30
Purchase #5	$42.45	11.439%	$47.3059	$47.31	$47.30	$47.30
Purchase #6	$151.36	5.618%	$159.8634	$159.86	$159.85	$159.90
Purchase #7	$31.70	12.779%	$35.7509	$35.75	$35.75	$35.80
7 purchase totals =	$568.87		$612.2179	$612.22	$612.20	$612.30