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	$168.27	10.245%	$185.5093	$185.51	$185.50	$185.50
Purchase #2	$119.43	8.774%	$129.9088	$129.91	$129.90	$129.90
Purchase #3	$141.40	11.229%	$157.2778	$157.28	$157.30	$157.30
Purchase #4	$93.80	6.413%	$99.8154	$99.82	$99.80	$99.80
Purchase #5	$244.95	7.563%	$263.4756	$263.48	$263.50	$263.50
Purchase #6	$231.89	11.376%	$258.2698	$258.27	$258.25	$258.30
Purchase #7	$230.93	7.654%	$248.6054	$248.61	$248.60	$248.60
7 purchase totals =	$1,230.67		$1,342.8621	$1,342.88	$1,342.85	$1,342.90