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	$135.65	8.324%	$146.9415	$146.94	$146.95	$146.90
Purchase #2	$135.89	6.543%	$144.7813	$144.78	$144.80	$144.80
Purchase #3	$156.97	9.250%	$171.4897	$171.49	$171.50	$171.50
Purchase #4	$61.40	13.166%	$69.4839	$69.48	$69.50	$69.50
Purchase #5	$170.91	8.618%	$185.639	$185.64	$185.65	$185.60
Purchase #6	$222.42	7.863%	$239.9089	$239.91	$239.90	$239.90
Purchase #7	$137.33	7.385%	$147.4718	$147.47	$147.45	$147.50
7 purchase totals =	$1,020.57		$1,105.7161	$1,105.71	$1,105.75	$1,105.70