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	$105.97	10.207%	$116.7864	$116.79	$116.80	$116.80
Purchase #2	$198.32	6.498%	$211.2068	$211.21	$211.20	$211.20
Purchase #3	$58.89	4.716%	$61.6673	$61.67	$61.65	$61.70
Purchase #4	$103.79	7.149%	$111.2099	$111.21	$111.20	$111.20
Purchase #5	$250.32	7.536%	$269.1841	$269.18	$269.20	$269.20
Purchase #6	$158.72	4.501%	$165.864	$165.86	$165.85	$165.90
Purchase #7	$155.78	9.729%	$170.9358	$170.94	$170.95	$170.90
7 purchase totals =	$1,031.79		$1,106.8543	$1,106.86	$1,106.85	$1,106.90