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	$63.48	3.351%	$65.6072	$65.61	$65.60	$65.60
Purchase #2	$38.32	8.378%	$41.5304	$41.53	$41.55	$41.50
Purchase #3	$80.56	10.634%	$89.1268	$89.13	$89.15	$89.10
Purchase #4	$101.64	11.241%	$113.0654	$113.07	$113.05	$113.10
Purchase #5	$105.72	8.124%	$114.3087	$114.31	$114.30	$114.30
Purchase #6	$57.70	6.184%	$61.2682	$61.27	$61.25	$61.30
Purchase #7	$150.55	13.253%	$170.5024	$170.50	$170.50	$170.50
7 purchase totals =	$597.97		$655.4091	$655.42	$655.40	$655.40