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	$55.50	7.473%	$59.6475	$59.65	$59.65	$59.60
Purchase #2	$210.88	10.532%	$233.0899	$233.09	$233.10	$233.10
Purchase #3	$79.29	3.624%	$82.1635	$82.16	$82.15	$82.20
Purchase #4	$38.95	3.692%	$40.388	$40.39	$40.40	$40.40
Purchase #5	$137.96	4.329%	$143.9323	$143.93	$143.95	$143.90
Purchase #6	$191.80	5.304%	$201.9731	$201.97	$201.95	$202.00
Purchase #7	$243.73	12.697%	$274.6764	$274.68	$274.70	$274.70
7 purchase totals =	$958.11		$1,035.8707	$1,035.87	$1,035.90	$1,035.90