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	$127.85	13.619%	$145.2619	$145.26	$145.25	$145.30
Purchase #2	$145.77	7.175%	$156.229	$156.23	$156.25	$156.20
Purchase #3	$80.72	7.680%	$86.9193	$86.92	$86.90	$86.90
Purchase #4	$77.67	9.358%	$84.9384	$84.94	$84.95	$84.90
Purchase #5	$134.35	12.811%	$151.5616	$151.56	$151.55	$151.60
Purchase #6	$80.82	13.104%	$91.4107	$91.41	$91.40	$91.40
Purchase #7	$111.40	7.637%	$119.9076	$119.91	$119.90	$119.90
7 purchase totals =	$758.58		$836.2285	$836.23	$836.20	$836.20