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	$68.37	3.766%	$70.9448	$70.94	$70.95	$70.90
Purchase #2	$84.94	3.427%	$87.8509	$87.85	$87.85	$87.90
Purchase #3	$243.29	5.375%	$256.3668	$256.37	$256.35	$256.40
Purchase #4	$52.26	13.690%	$59.4144	$59.41	$59.40	$59.40
Purchase #5	$156.39	12.295%	$175.6182	$175.62	$175.60	$175.60
Purchase #6	$234.65	10.386%	$259.0207	$259.02	$259.00	$259.00
Purchase #7	$143.85	10.766%	$159.3369	$159.34	$159.35	$159.30
7 purchase totals =	$983.75		$1,068.5527	$1,068.55	$1,068.50	$1,068.50