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	$43.86	5.287%	$46.1789	$46.18	$46.20	$46.20
Purchase #2	$105.72	5.726%	$111.7735	$111.77	$111.75	$111.80
Purchase #3	$123.79	11.504%	$138.0308	$138.03	$138.05	$138.00
Purchase #4	$223.33	6.282%	$237.3596	$237.36	$237.35	$237.40
Purchase #5	$48.64	3.791%	$50.4839	$50.48	$50.50	$50.50
Purchase #6	$92.51	11.602%	$103.243	$103.24	$103.25	$103.20
Purchase #7	$77.72	7.565%	$83.5995	$83.60	$83.60	$83.60
7 purchase totals =	$715.57		$770.6692	$770.66	$770.70	$770.70