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	$225.31	13.182%	$255.0104	$255.01	$255.00	$255.00
Purchase #2	$7.44	4.125%	$7.7469	$7.75	$7.75	$7.70
Purchase #3	$67.89	5.281%	$71.4753	$71.48	$71.50	$71.50
Purchase #4	$108.74	5.285%	$114.4869	$114.49	$114.50	$114.50
Purchase #5	$160.25	7.517%	$172.296	$172.30	$172.30	$172.30
Purchase #6	$51.83	3.339%	$53.5606	$53.56	$53.55	$53.60
Purchase #7	$235.57	9.571%	$258.1164	$258.12	$258.10	$258.10
7 purchase totals =	$857.03		$932.6925	$932.71	$932.70	$932.70