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	$235.87	3.417%	$243.9297	$243.93	$243.95	$243.90
Purchase #2	$116.81	4.176%	$121.688	$121.69	$121.70	$121.70
Purchase #3	$132.41	9.409%	$144.8685	$144.87	$144.85	$144.90
Purchase #4	$29.39	13.260%	$33.2871	$33.29	$33.30	$33.30
Purchase #5	$53.31	11.422%	$59.3991	$59.40	$59.40	$59.40
Purchase #6	$78.53	3.299%	$81.1207	$81.12	$81.10	$81.10
Purchase #7	$39.81	4.401%	$41.562	$41.56	$41.55	$41.60
7 purchase totals =	$686.13		$725.8551	$725.86	$725.85	$725.90