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	$104.25	11.425%	$116.1606	$116.16	$116.15	$116.20
Purchase #2	$133.59	3.386%	$138.1134	$138.11	$138.10	$138.10
Purchase #3	$40.80	4.696%	$42.716	$42.72	$42.70	$42.70
Purchase #4	$73.78	12.236%	$82.8077	$82.81	$82.80	$82.80
Purchase #5	$192.83	10.219%	$212.5353	$212.54	$212.55	$212.50
Purchase #6	$35.31	9.240%	$38.5726	$38.57	$38.55	$38.60
Purchase #7	$224.33	8.643%	$243.7188	$243.72	$243.70	$243.70
7 purchase totals =	$804.89		$874.6244	$874.63	$874.55	$874.60