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	$126.46	11.716%	$141.2761	$141.28	$141.30	$141.30
Purchase #2	$231.87	9.668%	$254.2872	$254.29	$254.30	$254.30
Purchase #3	$232.42	13.641%	$264.1244	$264.12	$264.10	$264.10
Purchase #4	$152.38	3.353%	$157.4893	$157.49	$157.50	$157.50
Purchase #5	$89.76	10.720%	$99.3823	$99.38	$99.40	$99.40
Purchase #6	$184.33	11.116%	$204.8201	$204.82	$204.80	$204.80
Purchase #7	$151.72	3.160%	$156.5144	$156.51	$156.50	$156.50
7 purchase totals =	$1,168.94		$1,277.8938	$1,277.89	$1,277.90	$1,277.90