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	$152.71	13.145%	$172.7837	$172.78	$172.80	$172.80
Purchase #2	$213.40	4.220%	$222.4055	$222.41	$222.40	$222.40
Purchase #3	$61.30	6.753%	$65.4396	$65.44	$65.45	$65.40
Purchase #4	$46.96	13.847%	$53.4626	$53.46	$53.45	$53.50
Purchase #5	$9.31	7.216%	$9.9818	$9.98	$10.00	$10.00
Purchase #6	$64.78	10.513%	$71.5903	$71.59	$71.60	$71.60
Purchase #7	$59.51	8.641%	$64.6523	$64.65	$64.65	$64.70
7 purchase totals =	$607.97		$660.3158	$660.31	$660.35	$660.40