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	$81.36	5.130%	$85.5338	$85.53	$85.55	$85.50
Purchase #2	$30.40	5.697%	$32.1319	$32.13	$32.15	$32.10
Purchase #3	$5.48	7.555%	$5.894	$5.89	$5.90	$5.90
Purchase #4	$58.97	11.181%	$65.5634	$65.56	$65.55	$65.60
Purchase #5	$197.66	5.557%	$208.644	$208.64	$208.65	$208.60
Purchase #6	$58.60	4.216%	$61.0706	$61.07	$61.05	$61.10
Purchase #7	$124.87	5.201%	$131.3645	$131.36	$131.35	$131.40
7 purchase totals =	$557.34		$590.2022	$590.18	$590.20	$590.20