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	$87.55	3.562%	$90.6685	$90.67	$90.65	$90.70
Purchase #2	$75.61	4.111%	$78.7183	$78.72	$78.70	$78.70
Purchase #3	$69.53	12.818%	$78.4424	$78.44	$78.45	$78.40
Purchase #4	$93.78	12.760%	$105.7463	$105.75	$105.75	$105.70
Purchase #5	$74.71	3.341%	$77.2061	$77.21	$77.20	$77.20
Purchase #6	$20.63	11.855%	$23.0757	$23.08	$23.10	$23.10
Purchase #7	$72.50	12.822%	$81.796	$81.80	$81.80	$81.80
7 purchase totals =	$494.31		$535.6533	$535.67	$535.65	$535.60