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	$136.66	11.147%	$151.8935	$151.89	$151.90	$151.90
Purchase #2	$71.29	12.107%	$79.9211	$79.92	$79.90	$79.90
Purchase #3	$47.32	4.195%	$49.3051	$49.31	$49.30	$49.30
Purchase #4	$66.74	6.617%	$71.1562	$71.16	$71.15	$71.20
Purchase #5	$242.81	3.168%	$250.5022	$250.50	$250.50	$250.50
Purchase #6	$105.43	8.739%	$114.6435	$114.64	$114.65	$114.60
Purchase #7	$35.32	5.843%	$37.3837	$37.38	$37.40	$37.40
7 purchase totals =	$705.57		$754.8053	$754.80	$754.80	$754.80