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	$236.59	3.741%	$245.4408	$245.44	$245.45	$245.40
Purchase #2	$125.85	3.505%	$130.261	$130.26	$130.25	$130.30
Purchase #3	$231.83	11.501%	$258.4928	$258.49	$258.50	$258.50
Purchase #4	$97.58	12.165%	$109.4506	$109.45	$109.45	$109.50
Purchase #5	$72.98	10.369%	$80.5473	$80.55	$80.55	$80.50
Purchase #6	$16.90	5.868%	$17.8917	$17.89	$17.90	$17.90
Purchase #7	$230.80	10.453%	$254.9255	$254.93	$254.95	$254.90
7 purchase totals =	$1,012.53		$1,097.0097	$1,097.01	$1,097.05	$1,097.00