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	$179.74	10.297%	$198.2478	$198.25	$198.25	$198.20
Purchase #2	$116.91	9.422%	$127.9253	$127.93	$127.95	$127.90
Purchase #3	$43.89	11.312%	$48.8548	$48.85	$48.85	$48.90
Purchase #4	$32.95	9.274%	$36.0058	$36.01	$36.00	$36.00
Purchase #5	$244.61	4.135%	$254.7246	$254.72	$254.70	$254.70
Purchase #6	$205.49	11.624%	$229.3762	$229.38	$229.40	$229.40
Purchase #7	$139.30	6.228%	$147.9756	$147.98	$148.00	$148.00
7 purchase totals =	$962.89		$1,043.1101	$1,043.12	$1,043.15	$1,043.10