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	$115.83	10.816%	$128.3582	$128.36	$128.35	$128.40
Purchase #2	$54.33	13.193%	$61.4978	$61.50	$61.50	$61.50
Purchase #3	$155.67	5.662%	$164.484	$164.48	$164.50	$164.50
Purchase #4	$13.62	12.619%	$15.3387	$15.34	$15.35	$15.30
Purchase #5	$46.61	3.241%	$48.1206	$48.12	$48.10	$48.10
Purchase #6	$157.75	13.574%	$179.163	$179.16	$179.15	$179.20
Purchase #7	$74.50	5.784%	$78.8091	$78.81	$78.80	$78.80
7 purchase totals =	$618.31		$675.7714	$675.77	$675.75	$675.80