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	$214.80	9.634%	$235.4938	$235.49	$235.50	$235.50
Purchase #2	$207.33	6.190%	$220.1637	$220.16	$220.15	$220.20
Purchase #3	$124.69	9.785%	$136.8909	$136.89	$136.90	$136.90
Purchase #4	$67.41	8.109%	$72.8763	$72.88	$72.90	$72.90
Purchase #5	$99.50	5.303%	$104.7765	$104.78	$104.80	$104.80
Purchase #6	$25.83	11.624%	$28.8325	$28.83	$28.85	$28.80
Purchase #7	$72.48	9.414%	$79.3033	$79.30	$79.30	$79.30
7 purchase totals =	$812.04		$878.3370	$878.33	$878.40	$878.40