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	$75.73	3.558%	$78.4245	$78.42	$78.40	$78.40
Purchase #2	$89.68	6.392%	$95.4123	$95.41	$95.40	$95.40
Purchase #3	$43.30	13.717%	$49.2395	$49.24	$49.25	$49.20
Purchase #4	$187.48	11.341%	$208.7421	$208.74	$208.75	$208.70
Purchase #5	$101.77	9.403%	$111.3394	$111.34	$111.35	$111.30
Purchase #6	$225.55	4.394%	$235.4607	$235.46	$235.45	$235.50
Purchase #7	$245.75	11.481%	$273.9646	$273.96	$273.95	$274.00
7 purchase totals =	$969.26		$1,052.5831	$1,052.57	$1,052.55	$1,052.50