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	$198.37	6.592%	$211.4466	$211.45	$211.45	$211.40
Purchase #2	$146.66	13.272%	$166.1247	$166.12	$166.10	$166.10
Purchase #3	$134.51	13.306%	$152.4079	$152.41	$152.40	$152.40
Purchase #4	$6.74	7.146%	$7.2216	$7.22	$7.20	$7.20
Purchase #5	$216.93	5.851%	$229.6226	$229.62	$229.60	$229.60
Purchase #6	$160.61	7.598%	$172.8131	$172.81	$172.80	$172.80
Purchase #7	$80.76	13.582%	$91.7288	$91.73	$91.75	$91.70
7 purchase totals =	$944.58		$1,031.3653	$1,031.36	$1,031.30	$1,031.20