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	$119.44	11.677%	$133.387	$133.39	$133.40	$133.40
Purchase #2	$244.51	12.666%	$275.4796	$275.48	$275.50	$275.50
Purchase #3	$28.76	12.616%	$32.3884	$32.39	$32.40	$32.40
Purchase #4	$141.70	12.554%	$159.489	$159.49	$159.50	$159.50
Purchase #5	$211.78	6.485%	$225.5139	$225.51	$225.50	$225.50
Purchase #6	$54.74	8.482%	$59.383	$59.38	$59.40	$59.40
Purchase #7	$188.67	11.741%	$210.8217	$210.82	$210.80	$210.80
7 purchase totals =	$989.60		$1,096.4626	$1,096.46	$1,096.50	$1,096.50