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	$197.64	9.350%	$216.1193	$216.12	$216.10	$216.10
Purchase #2	$161.59	13.802%	$183.8927	$183.89	$183.90	$183.90
Purchase #3	$152.54	3.536%	$157.9338	$157.93	$157.95	$157.90
Purchase #4	$81.73	9.814%	$89.751	$89.75	$89.75	$89.80
Purchase #5	$60.57	7.560%	$65.1491	$65.15	$65.15	$65.10
Purchase #6	$156.94	10.178%	$172.9134	$172.91	$172.90	$172.90
Purchase #7	$246.91	6.578%	$263.1517	$263.15	$263.15	$263.20
7 purchase totals =	$1,057.92		$1,148.9110	$1,148.90	$1,148.90	$1,148.90