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	$41.51	13.174%	$46.9785	$46.98	$47.00	$47.00
Purchase #2	$58.27	12.392%	$65.4908	$65.49	$65.50	$65.50
Purchase #3	$61.39	7.577%	$66.0415	$66.04	$66.05	$66.00
Purchase #4	$243.76	12.746%	$274.8296	$274.83	$274.85	$274.80
Purchase #5	$250.94	3.819%	$260.5234	$260.52	$260.50	$260.50
Purchase #6	$73.67	12.862%	$83.1454	$83.15	$83.15	$83.10
Purchase #7	$33.89	12.499%	$38.1259	$38.13	$38.15	$38.10
7 purchase totals =	$763.43		$835.1351	$835.14	$835.20	$835.00