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	$230.47	7.506%	$247.7691	$247.77	$247.75	$247.80
Purchase #2	$57.58	6.605%	$61.3832	$61.38	$61.40	$61.40
Purchase #3	$116.87	13.705%	$132.887	$132.89	$132.90	$132.90
Purchase #4	$38.95	9.271%	$42.5611	$42.56	$42.55	$42.60
Purchase #5	$39.38	8.819%	$42.8529	$42.85	$42.85	$42.90
Purchase #6	$7.41	9.501%	$8.114	$8.11	$8.10	$8.10
Purchase #7	$136.81	7.818%	$147.5058	$147.51	$147.50	$147.50
7 purchase totals =	$627.47		$683.0731	$683.07	$683.05	$683.20