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	$55.72	6.715%	$59.4616	$59.46	$59.45	$59.50
Purchase #2	$248.59	4.734%	$260.3583	$260.36	$260.35	$260.40
Purchase #3	$52.38	11.686%	$58.5011	$58.50	$58.50	$58.50
Purchase #4	$156.81	13.458%	$177.9135	$177.91	$177.90	$177.90
Purchase #5	$58.77	4.274%	$61.2818	$61.28	$61.30	$61.30
Purchase #6	$189.87	7.706%	$204.5014	$204.50	$204.50	$204.50
Purchase #7	$67.87	3.544%	$70.2753	$70.28	$70.30	$70.30
7 purchase totals =	$830.01		$892.2930	$892.29	$892.30	$892.40