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	$57.27	3.549%	$59.3025	$59.30	$59.30	$59.30
Purchase #2	$213.65	5.737%	$225.9071	$225.91	$225.90	$225.90
Purchase #3	$17.42	3.444%	$18.0199	$18.02	$18.00	$18.00
Purchase #4	$33.58	3.683%	$34.8168	$34.82	$34.80	$34.80
Purchase #5	$39.64	7.298%	$42.5329	$42.53	$42.55	$42.50
Purchase #6	$248.89	3.673%	$258.0317	$258.03	$258.05	$258.00
Purchase #7	$99.69	7.735%	$107.401	$107.40	$107.40	$107.40
7 purchase totals =	$710.14		$746.0119	$746.01	$746.00	$745.90