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	$146.42	3.358%	$151.3368	$151.34	$151.35	$151.30
Purchase #2	$243.96	4.510%	$254.9626	$254.96	$254.95	$255.00
Purchase #3	$101.39	4.731%	$106.1868	$106.19	$106.20	$106.20
Purchase #4	$222.97	6.359%	$237.1487	$237.15	$237.15	$237.10
Purchase #5	$10.93	8.473%	$11.8561	$11.86	$11.85	$11.90
Purchase #6	$127.71	11.215%	$142.0327	$142.03	$142.05	$142.00
Purchase #7	$101.96	13.640%	$115.8673	$115.87	$115.85	$115.90
7 purchase totals =	$955.34		$1,019.3910	$1,019.40	$1,019.40	$1,019.40