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	$38.88	7.411%	$41.7614	$41.76	$41.75	$41.80
Purchase #2	$122.50	6.837%	$130.8753	$130.88	$130.90	$130.90
Purchase #3	$134.43	10.262%	$148.2252	$148.23	$148.25	$148.20
Purchase #4	$171.87	7.490%	$184.7431	$184.74	$184.75	$184.70
Purchase #5	$165.58	9.842%	$181.8764	$181.88	$181.90	$181.90
Purchase #6	$238.92	13.237%	$270.5458	$270.55	$270.55	$270.50
Purchase #7	$83.48	8.300%	$90.4088	$90.41	$90.40	$90.40
7 purchase totals =	$955.66		$1,048.4360	$1,048.45	$1,048.50	$1,048.40