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	$97.45	4.331%	$101.6706	$101.67	$101.65	$101.70
Purchase #2	$77.56	6.581%	$82.6642	$82.66	$82.65	$82.70
Purchase #3	$127.80	11.183%	$142.0919	$142.09	$142.10	$142.10
Purchase #4	$182.32	11.438%	$203.1738	$203.17	$203.15	$203.20
Purchase #5	$99.48	5.574%	$105.025	$105.03	$105.05	$105.00
Purchase #6	$77.64	9.770%	$85.2254	$85.23	$85.25	$85.20
Purchase #7	$85.81	13.382%	$97.2931	$97.29	$97.30	$97.30
7 purchase totals =	$748.06		$817.1440	$817.14	$817.15	$817.20