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	$125.53	4.820%	$131.5805	$131.58	$131.60	$131.60
Purchase #2	$233.63	6.126%	$247.9422	$247.94	$247.95	$247.90
Purchase #3	$105.55	12.692%	$118.9464	$118.95	$118.95	$118.90
Purchase #4	$225.81	6.793%	$241.1493	$241.15	$241.15	$241.10
Purchase #5	$105.52	7.739%	$113.6862	$113.69	$113.70	$113.70
Purchase #6	$246.41	9.534%	$269.9027	$269.90	$269.90	$269.90
Purchase #7	$22.72	11.399%	$25.3099	$25.31	$25.30	$25.30
7 purchase totals =	$1,065.17		$1,148.5172	$1,148.52	$1,148.55	$1,148.40