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	$121.66	7.113%	$130.3137	$130.31	$130.30	$130.30
Purchase #2	$99.71	13.582%	$113.2526	$113.25	$113.25	$113.30
Purchase #3	$226.33	12.343%	$254.2659	$254.27	$254.25	$254.30
Purchase #4	$40.48	9.634%	$44.3798	$44.38	$44.40	$44.40
Purchase #5	$164.35	11.175%	$182.7161	$182.72	$182.70	$182.70
Purchase #6	$108.32	3.365%	$111.965	$111.97	$111.95	$112.00
Purchase #7	$212.60	13.356%	$240.9949	$240.99	$241.00	$241.00
7 purchase totals =	$973.45		$1,077.8880	$1,077.89	$1,077.85	$1,078.00