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	$216.32	9.507%	$236.8855	$236.89	$236.90	$236.90
Purchase #2	$73.51	9.758%	$80.6831	$80.68	$80.70	$80.70
Purchase #3	$93.79	11.385%	$104.468	$104.47	$104.45	$104.50
Purchase #4	$48.43	8.859%	$52.7204	$52.72	$52.70	$52.70
Purchase #5	$64.77	11.676%	$72.3325	$72.33	$72.35	$72.30
Purchase #6	$34.38	13.141%	$38.8979	$38.90	$38.90	$38.90
Purchase #7	$167.39	12.782%	$188.7858	$188.79	$188.80	$188.80
7 purchase totals =	$698.59		$774.7732	$774.78	$774.80	$774.80