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	$221.36	12.802%	$249.6985	$249.70	$249.70	$249.70
Purchase #2	$199.39	10.219%	$219.7657	$219.77	$219.75	$219.80
Purchase #3	$200.80	10.481%	$221.8458	$221.85	$221.85	$221.80
Purchase #4	$122.29	7.445%	$131.3945	$131.39	$131.40	$131.40
Purchase #5	$230.63	5.803%	$244.0135	$244.01	$244.00	$244.00
Purchase #6	$49.69	7.169%	$53.2523	$53.25	$53.25	$53.30
Purchase #7	$99.33	6.167%	$105.4557	$105.46	$105.45	$105.50
7 purchase totals =	$1,123.49		$1,225.4260	$1,225.43	$1,225.40	$1,225.50