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	$62.83	9.234%	$68.6317	$68.63	$68.65	$68.60
Purchase #2	$40.27	3.531%	$41.6919	$41.69	$41.70	$41.70
Purchase #3	$136.70	13.169%	$154.702	$154.70	$154.70	$154.70
Purchase #4	$195.55	13.836%	$222.6063	$222.61	$222.60	$222.60
Purchase #5	$210.66	5.574%	$222.4022	$222.40	$222.40	$222.40
Purchase #6	$37.46	6.468%	$39.8829	$39.88	$39.90	$39.90
Purchase #7	$248.74	7.523%	$267.4527	$267.45	$267.45	$267.50
7 purchase totals =	$932.21		$1,017.3697	$1,017.36	$1,017.40	$1,017.40