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	$223.44	8.242%	$241.8559	$241.86	$241.85	$241.90
Purchase #2	$16.86	11.493%	$18.7977	$18.80	$18.80	$18.80
Purchase #3	$104.56	11.722%	$116.8165	$116.82	$116.80	$116.80
Purchase #4	$184.69	7.143%	$197.8824	$197.88	$197.90	$197.90
Purchase #5	$133.47	12.621%	$150.3152	$150.32	$150.30	$150.30
Purchase #6	$240.49	9.162%	$262.5237	$262.52	$262.50	$262.50
Purchase #7	$58.80	12.415%	$66.1	$66.10	$66.10	$66.10
7 purchase totals =	$962.31		$1,054.2914	$1,054.30	$1,054.25	$1,054.30