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	$64.68	11.273%	$71.9714	$71.97	$71.95	$72.00
Purchase #2	$59.65	12.172%	$66.9106	$66.91	$66.90	$66.90
Purchase #3	$32.54	10.113%	$35.8308	$35.83	$35.85	$35.80
Purchase #4	$42.27	13.133%	$47.8213	$47.82	$47.80	$47.80
Purchase #5	$170.26	8.293%	$184.3797	$184.38	$184.40	$184.40
Purchase #6	$234.51	8.111%	$253.5311	$253.53	$253.55	$253.50
Purchase #7	$61.29	9.190%	$66.9226	$66.92	$66.90	$66.90
7 purchase totals =	$665.20		$727.3675	$727.36	$727.35	$727.30