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	$149.42	9.817%	$164.0886	$164.09	$164.10	$164.10
Purchase #2	$33.51	11.817%	$37.4699	$37.47	$37.45	$37.50
Purchase #3	$101.30	4.345%	$105.7015	$105.70	$105.70	$105.70
Purchase #4	$173.29	11.313%	$192.8943	$192.89	$192.90	$192.90
Purchase #5	$65.77	3.868%	$68.314	$68.31	$68.30	$68.30
Purchase #6	$185.79	13.619%	$211.0927	$211.09	$211.10	$211.10
Purchase #7	$25.35	12.539%	$28.5286	$28.53	$28.55	$28.50
7 purchase totals =	$734.43		$808.0896	$808.08	$808.10	$808.10