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	$59.85	4.617%	$62.6133	$62.61	$62.60	$62.60
Purchase #2	$86.26	3.298%	$89.1049	$89.10	$89.10	$89.10
Purchase #3	$123.67	3.575%	$128.0912	$128.09	$128.10	$128.10
Purchase #4	$120.98	4.521%	$126.4495	$126.45	$126.45	$126.40
Purchase #5	$62.41	4.358%	$65.1298	$65.13	$65.15	$65.10
Purchase #6	$199.36	3.375%	$206.0884	$206.09	$206.10	$206.10
Purchase #7	$244.38	3.814%	$253.7007	$253.70	$253.70	$253.70
7 purchase totals =	$896.91		$931.1778	$931.17	$931.20	$931.10