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	$232.59	9.160%	$253.8952	$253.90	$253.90	$253.90
Purchase #2	$59.58	12.388%	$66.9608	$66.96	$66.95	$67.00
Purchase #3	$127.30	7.130%	$136.3765	$136.38	$136.40	$136.40
Purchase #4	$230.61	5.335%	$242.913	$242.91	$242.90	$242.90
Purchase #5	$170.99	10.386%	$188.749	$188.75	$188.75	$188.70
Purchase #6	$63.57	4.414%	$66.376	$66.38	$66.40	$66.40
Purchase #7	$43.91	7.285%	$47.1088	$47.11	$47.10	$47.10
7 purchase totals =	$928.55		$1,002.3793	$1,002.39	$1,002.40	$1,002.40