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	$114.34	12.427%	$128.549	$128.55	$128.55	$128.50
Purchase #2	$202.85	9.575%	$222.2729	$222.27	$222.25	$222.30
Purchase #3	$135.86	3.560%	$140.6966	$140.70	$140.70	$140.70
Purchase #4	$213.77	13.656%	$242.9624	$242.96	$242.95	$243.00
Purchase #5	$134.65	12.762%	$151.834	$151.83	$151.85	$151.80
Purchase #6	$139.76	3.775%	$145.0359	$145.04	$145.05	$145.00
Purchase #7	$218.58	6.848%	$233.5484	$233.55	$233.55	$233.50
7 purchase totals =	$1,159.81		$1,264.8992	$1,264.90	$1,264.90	$1,264.80