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	$131.67	9.125%	$143.6849	$143.68	$143.70	$143.70
Purchase #2	$202.25	11.192%	$224.8858	$224.89	$224.90	$224.90
Purchase #3	$83.37	6.676%	$88.9358	$88.94	$88.95	$88.90
Purchase #4	$58.79	6.843%	$62.813	$62.81	$62.80	$62.80
Purchase #5	$135.46	3.148%	$139.7243	$139.72	$139.70	$139.70
Purchase #6	$248.77	6.486%	$264.9052	$264.91	$264.90	$264.90
Purchase #7	$249.47	10.587%	$275.8814	$275.88	$275.90	$275.90
7 purchase totals =	$1,109.78		$1,200.8304	$1,200.83	$1,200.85	$1,200.80