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	$100.45	12.309%	$112.8144	$112.81	$112.80	$112.80
Purchase #2	$221.85	8.319%	$240.3057	$240.31	$240.30	$240.30
Purchase #3	$40.48	5.168%	$42.572	$42.57	$42.55	$42.60
Purchase #4	$99.44	5.599%	$105.0076	$105.01	$105.00	$105.00
Purchase #5	$224.38	13.297%	$254.2158	$254.22	$254.20	$254.20
Purchase #6	$130.40	13.860%	$148.4734	$148.47	$148.45	$148.50
Purchase #7	$117.64	3.488%	$121.7433	$121.74	$121.75	$121.70
7 purchase totals =	$934.64		$1,025.1322	$1,025.13	$1,025.05	$1,025.10