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	$207.39	9.396%	$226.8764	$226.88	$226.90	$226.90
Purchase #2	$110.77	11.692%	$123.7212	$123.72	$123.70	$123.70
Purchase #3	$151.73	8.164%	$164.1172	$164.12	$164.10	$164.10
Purchase #4	$123.38	12.805%	$139.1788	$139.18	$139.20	$139.20
Purchase #5	$10.90	7.549%	$11.7228	$11.72	$11.70	$11.70
Purchase #6	$175.98	11.631%	$196.4482	$196.45	$196.45	$196.40
Purchase #7	$188.81	3.554%	$195.5203	$195.52	$195.50	$195.50
7 purchase totals =	$968.96		$1,057.5849	$1,057.59	$1,057.55	$1,057.50