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	$152.52	8.434%	$165.3835	$165.38	$165.40	$165.40
Purchase #2	$216.33	4.222%	$225.4635	$225.46	$225.45	$225.50
Purchase #3	$33.76	11.782%	$37.7376	$37.74	$37.75	$37.70
Purchase #4	$67.38	5.773%	$71.2698	$71.27	$71.25	$71.30
Purchase #5	$43.34	6.723%	$46.2537	$46.25	$46.25	$46.30
Purchase #6	$97.96	6.629%	$104.4538	$104.45	$104.45	$104.50
Purchase #7	$212.81	5.507%	$224.5294	$224.53	$224.55	$224.50
7 purchase totals =	$824.10		$875.0913	$875.08	$875.10	$875.20