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	$213.73	12.367%	$240.162	$240.16	$240.15	$240.20
Purchase #2	$36.29	10.642%	$40.152	$40.15	$40.15	$40.20
Purchase #3	$36.66	10.266%	$40.4235	$40.42	$40.40	$40.40
Purchase #4	$111.86	6.860%	$119.5336	$119.53	$119.55	$119.50
Purchase #5	$7.46	4.469%	$7.7934	$7.79	$7.80	$7.80
Purchase #6	$55.47	12.761%	$62.5485	$62.55	$62.55	$62.50
Purchase #7	$242.59	3.698%	$251.561	$251.56	$251.55	$251.60
7 purchase totals =	$704.06		$762.1740	$762.16	$762.15	$762.20