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	$35.26	7.352%	$37.8523	$37.85	$37.85	$37.90
Purchase #2	$82.96	9.127%	$90.5318	$90.53	$90.55	$90.50
Purchase #3	$51.92	8.135%	$56.1437	$56.14	$56.15	$56.10
Purchase #4	$89.62	11.121%	$99.5866	$99.59	$99.60	$99.60
Purchase #5	$215.46	12.386%	$242.1469	$242.15	$242.15	$242.10
Purchase #6	$100.78	5.811%	$106.6363	$106.64	$106.65	$106.60
Purchase #7	$135.47	13.580%	$153.8668	$153.87	$153.85	$153.90
7 purchase totals =	$711.47		$786.7644	$786.77	$786.80	$786.70