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	$248.93	7.614%	$267.8835	$267.88	$267.90	$267.90
Purchase #2	$78.50	13.685%	$89.2427	$89.24	$89.25	$89.20
Purchase #3	$230.34	7.501%	$247.6178	$247.62	$247.60	$247.60
Purchase #4	$111.39	4.598%	$116.5117	$116.51	$116.50	$116.50
Purchase #5	$35.44	3.689%	$36.7474	$36.75	$36.75	$36.70
Purchase #6	$45.46	13.217%	$51.4684	$51.47	$51.45	$51.50
Purchase #7	$218.66	10.163%	$240.8824	$240.88	$240.90	$240.90
7 purchase totals =	$968.72		$1,050.3539	$1,050.35	$1,050.35	$1,050.30