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	$53.84	13.678%	$61.2042	$61.20	$61.20	$61.20
Purchase #2	$123.25	13.190%	$139.5067	$139.51	$139.50	$139.50
Purchase #3	$133.86	12.130%	$150.0972	$150.10	$150.10	$150.10
Purchase #4	$180.62	8.738%	$196.4026	$196.40	$196.40	$196.40
Purchase #5	$200.83	7.754%	$216.4024	$216.40	$216.40	$216.40
Purchase #6	$233.94	10.845%	$259.3108	$259.31	$259.30	$259.30
Purchase #7	$171.86	7.457%	$184.6756	$184.68	$184.70	$184.70
7 purchase totals =	$1,098.20		$1,207.5995	$1,207.60	$1,207.60	$1,207.60