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	$94.58	9.835%	$103.8819	$103.88	$103.90	$103.90
Purchase #2	$131.80	4.321%	$137.4951	$137.50	$137.50	$137.50
Purchase #3	$117.91	11.431%	$131.3883	$131.39	$131.40	$131.40
Purchase #4	$150.37	9.807%	$165.1168	$165.12	$165.10	$165.10
Purchase #5	$221.66	8.142%	$239.7076	$239.71	$239.70	$239.70
Purchase #6	$55.26	13.132%	$62.5167	$62.52	$62.50	$62.50
Purchase #7	$222.78	9.484%	$243.9085	$243.91	$243.90	$243.90
7 purchase totals =	$994.36		$1,084.0149	$1,084.03	$1,084.00	$1,084.00