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	$143.66	5.751%	$151.9219	$151.92	$151.90	$151.90
Purchase #2	$171.62	8.312%	$185.8851	$185.89	$185.90	$185.90
Purchase #3	$39.89	8.810%	$43.4043	$43.40	$43.40	$43.40
Purchase #4	$250.58	10.344%	$276.5	$276.50	$276.50	$276.50
Purchase #5	$35.98	3.423%	$37.2116	$37.21	$37.20	$37.20
Purchase #6	$185.67	8.684%	$201.7936	$201.79	$201.80	$201.80
Purchase #7	$59.37	5.179%	$62.4448	$62.44	$62.45	$62.40
7 purchase totals =	$886.77		$959.1613	$959.15	$959.15	$959.10