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	$228.53	12.180%	$256.365	$256.37	$256.35	$256.40
Purchase #2	$148.34	13.860%	$168.8999	$168.90	$168.90	$168.90
Purchase #3	$201.56	5.718%	$213.0852	$213.09	$213.10	$213.10
Purchase #4	$108.26	11.672%	$120.8961	$120.90	$120.90	$120.90
Purchase #5	$56.53	8.434%	$61.2977	$61.30	$61.30	$61.30
Purchase #6	$82.66	3.251%	$85.3473	$85.35	$85.35	$85.30
Purchase #7	$151.40	11.378%	$168.6263	$168.63	$168.65	$168.60
7 purchase totals =	$977.28		$1,074.5175	$1,074.54	$1,074.55	$1,074.50