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	$80.87	13.840%	$92.0624	$92.06	$92.05	$92.10
Purchase #2	$153.53	7.721%	$165.3841	$165.38	$165.40	$165.40
Purchase #3	$163.56	10.589%	$180.8794	$180.88	$180.90	$180.90
Purchase #4	$54.58	13.217%	$61.7938	$61.79	$61.80	$61.80
Purchase #5	$144.70	3.331%	$149.52	$149.52	$149.50	$149.50
Purchase #6	$133.52	4.749%	$139.8609	$139.86	$139.85	$139.90
Purchase #7	$218.67	4.234%	$227.9285	$227.93	$227.95	$227.90
7 purchase totals =	$949.43		$1,017.4291	$1,017.42	$1,017.45	$1,017.50