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	$56.35	7.324%	$60.4771	$60.48	$60.50	$60.50
Purchase #2	$85.73	4.528%	$89.6119	$89.61	$89.60	$89.60
Purchase #3	$43.42	3.694%	$45.0239	$45.02	$45.00	$45.00
Purchase #4	$48.86	8.601%	$53.0624	$53.06	$53.05	$53.10
Purchase #5	$110.43	5.334%	$116.3203	$116.32	$116.30	$116.30
Purchase #6	$34.65	8.238%	$37.5045	$37.50	$37.50	$37.50
Purchase #7	$188.65	12.791%	$212.7802	$212.78	$212.80	$212.80
7 purchase totals =	$568.09		$614.7803	$614.77	$614.75	$614.80