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	$235.67	7.734%	$253.8967	$253.90	$253.90	$253.90
Purchase #2	$89.28	6.335%	$94.9359	$94.94	$94.95	$94.90
Purchase #3	$41.80	8.160%	$45.2109	$45.21	$45.20	$45.20
Purchase #4	$131.63	12.517%	$148.1061	$148.11	$148.10	$148.10
Purchase #5	$234.33	12.110%	$262.7074	$262.71	$262.70	$262.70
Purchase #6	$161.39	10.648%	$178.5748	$178.57	$178.55	$178.60
Purchase #7	$131.79	9.597%	$144.4379	$144.44	$144.45	$144.40
7 purchase totals =	$1,025.89		$1,127.8697	$1,127.88	$1,127.85	$1,127.80