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	$181.40	13.617%	$206.1012	$206.10	$206.10	$206.10
Purchase #2	$127.86	10.413%	$141.1741	$141.17	$141.15	$141.20
Purchase #3	$45.81	12.148%	$51.375	$51.38	$51.40	$51.40
Purchase #4	$155.28	3.494%	$160.7055	$160.71	$160.70	$160.70
Purchase #5	$111.88	11.243%	$124.4587	$124.46	$124.45	$124.50
Purchase #6	$26.52	3.612%	$27.4779	$27.48	$27.50	$27.50
Purchase #7	$248.29	10.194%	$273.6007	$273.60	$273.60	$273.60
7 purchase totals =	$897.04		$984.8931	$984.90	$984.90	$985.00