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	$110.62	5.785%	$117.0194	$117.02	$117.00	$117.00
Purchase #2	$141.76	8.162%	$153.3305	$153.33	$153.35	$153.30
Purchase #3	$154.84	11.404%	$172.498	$172.50	$172.50	$172.50
Purchase #4	$116.92	8.742%	$127.1411	$127.14	$127.15	$127.10
Purchase #5	$50.48	10.569%	$55.8152	$55.82	$55.80	$55.80
Purchase #6	$232.36	9.736%	$254.9826	$254.98	$255.00	$255.00
Purchase #7	$13.82	7.134%	$14.8059	$14.81	$14.80	$14.80
7 purchase totals =	$820.80		$895.5927	$895.60	$895.60	$895.50