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	$65.76	4.578%	$68.7705	$68.77	$68.75	$68.80
Purchase #2	$64.72	10.581%	$71.568	$71.57	$71.55	$71.60
Purchase #3	$126.85	9.640%	$139.0783	$139.08	$139.10	$139.10
Purchase #4	$49.67	11.489%	$55.3766	$55.38	$55.40	$55.40
Purchase #5	$58.39	13.562%	$66.3089	$66.31	$66.30	$66.30
Purchase #6	$134.91	12.421%	$151.6672	$151.67	$151.65	$151.70
Purchase #7	$172.87	4.650%	$180.9085	$180.91	$180.90	$180.90
7 purchase totals =	$673.17		$733.6780	$733.69	$733.65	$733.80