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	$229.57	9.561%	$251.5192	$251.52	$251.50	$251.50
Purchase #2	$241.71	5.726%	$255.5503	$255.55	$255.55	$255.60
Purchase #3	$32.80	9.281%	$35.8442	$35.84	$35.85	$35.80
Purchase #4	$121.36	4.249%	$126.5166	$126.52	$126.50	$126.50
Purchase #5	$175.69	13.216%	$198.9092	$198.91	$198.90	$198.90
Purchase #6	$18.27	3.559%	$18.9202	$18.92	$18.90	$18.90
Purchase #7	$33.78	12.689%	$38.0663	$38.07	$38.05	$38.10
7 purchase totals =	$853.18		$925.3260	$925.33	$925.25	$925.30