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	$161.53	5.407%	$170.2639	$170.26	$170.25	$170.30
Purchase #2	$173.44	13.383%	$196.6515	$196.65	$196.65	$196.70
Purchase #3	$238.59	12.619%	$268.6977	$268.70	$268.70	$268.70
Purchase #4	$236.53	4.406%	$246.9515	$246.95	$246.95	$247.00
Purchase #5	$177.64	10.594%	$196.4592	$196.46	$196.45	$196.50
Purchase #6	$36.66	11.511%	$40.8799	$40.88	$40.90	$40.90
Purchase #7	$70.42	3.451%	$72.8502	$72.85	$72.85	$72.90
7 purchase totals =	$1,094.81		$1,192.7539	$1,192.75	$1,192.75	$1,193.00