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	$147.88	6.326%	$157.2349	$157.23	$157.25	$157.20
Purchase #2	$204.25	9.126%	$222.8899	$222.89	$222.90	$222.90
Purchase #3	$222.26	8.782%	$241.7789	$241.78	$241.80	$241.80
Purchase #4	$133.63	5.120%	$140.4719	$140.47	$140.45	$140.50
Purchase #5	$198.77	11.316%	$221.2628	$221.26	$221.25	$221.30
Purchase #6	$201.30	10.308%	$222.05	$222.05	$222.05	$222.10
Purchase #7	$69.29	13.811%	$78.8596	$78.86	$78.85	$78.90
7 purchase totals =	$1,177.38		$1,284.5480	$1,284.54	$1,284.55	$1,284.70