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	$93.67	7.755%	$100.9341	$100.93	$100.95	$100.90
Purchase #2	$12.50	6.283%	$13.2854	$13.29	$13.30	$13.30
Purchase #3	$205.28	8.784%	$223.3118	$223.31	$223.30	$223.30
Purchase #4	$172.30	4.393%	$179.8691	$179.87	$179.85	$179.90
Purchase #5	$236.31	6.357%	$251.3322	$251.33	$251.35	$251.30
Purchase #6	$241.33	10.443%	$266.5321	$266.53	$266.55	$266.50
Purchase #7	$175.66	5.426%	$185.1913	$185.19	$185.20	$185.20
7 purchase totals =	$1,137.05		$1,220.4560	$1,220.45	$1,220.50	$1,220.40