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	$222.78	9.126%	$243.1109	$243.11	$243.10	$243.10
Purchase #2	$207.52	7.381%	$222.8371	$222.84	$222.85	$222.80
Purchase #3	$237.48	9.686%	$260.4823	$260.48	$260.50	$260.50
Purchase #4	$154.53	11.415%	$172.1696	$172.17	$172.15	$172.20
Purchase #5	$36.66	7.235%	$39.3124	$39.31	$39.30	$39.30
Purchase #6	$105.93	4.815%	$111.0305	$111.03	$111.05	$111.00
Purchase #7	$248.44	4.263%	$259.031	$259.03	$259.05	$259.00
7 purchase totals =	$1,213.34		$1,307.9738	$1,307.97	$1,308.00	$1,307.90