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	$106.45	9.713%	$116.7895	$116.79	$116.80	$116.80
Purchase #2	$166.39	8.761%	$180.9674	$180.97	$180.95	$181.00
Purchase #3	$53.94	5.243%	$56.7681	$56.77	$56.75	$56.80
Purchase #4	$128.44	8.811%	$139.7568	$139.76	$139.75	$139.80
Purchase #5	$217.61	4.511%	$227.4264	$227.43	$227.45	$227.40
Purchase #6	$110.27	11.733%	$123.208	$123.21	$123.20	$123.20
Purchase #7	$169.72	6.303%	$180.4175	$180.42	$180.40	$180.40
7 purchase totals =	$952.82		$1,025.3337	$1,025.35	$1,025.30	$1,025.40