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	$101.47	12.224%	$113.8737	$113.87	$113.85	$113.90
Purchase #2	$51.58	6.420%	$54.8914	$54.89	$54.90	$54.90
Purchase #3	$57.48	6.481%	$61.2053	$61.21	$61.20	$61.20
Purchase #4	$158.79	3.847%	$164.8987	$164.90	$164.90	$164.90
Purchase #5	$194.48	7.741%	$209.5347	$209.53	$209.55	$209.50
Purchase #6	$114.82	7.697%	$123.6577	$123.66	$123.65	$123.70
Purchase #7	$155.77	12.781%	$175.679	$175.68	$175.70	$175.70
7 purchase totals =	$834.39		$903.7405	$903.74	$903.75	$903.80