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	$203.28	4.817%	$213.072	$213.07	$213.05	$213.10
Purchase #2	$136.52	11.335%	$151.9945	$151.99	$152.00	$152.00
Purchase #3	$228.92	6.375%	$243.5137	$243.51	$243.50	$243.50
Purchase #4	$32.39	12.511%	$36.4423	$36.44	$36.45	$36.40
Purchase #5	$95.39	5.801%	$100.9236	$100.92	$100.90	$100.90
Purchase #6	$78.94	5.783%	$83.5051	$83.51	$83.50	$83.50
Purchase #7	$129.32	5.497%	$136.4287	$136.43	$136.45	$136.40
7 purchase totals =	$904.76		$965.8799	$965.87	$965.85	$965.80