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	$231.29	3.847%	$240.1877	$240.19	$240.20	$240.20
Purchase #2	$67.34	7.772%	$72.5737	$72.57	$72.55	$72.60
Purchase #3	$214.64	5.239%	$225.885	$225.89	$225.90	$225.90
Purchase #4	$234.72	11.179%	$260.9593	$260.96	$260.95	$261.00
Purchase #5	$53.92	13.705%	$61.3097	$61.31	$61.30	$61.30
Purchase #6	$236.43	4.580%	$247.2585	$247.26	$247.25	$247.30
Purchase #7	$141.95	13.691%	$161.3844	$161.38	$161.40	$161.40
7 purchase totals =	$1,180.29		$1,269.5583	$1,269.56	$1,269.55	$1,269.70