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	$218.53	13.301%	$247.5967	$247.60	$247.60	$247.60
Purchase #2	$40.35	12.380%	$45.3453	$45.35	$45.35	$45.30
Purchase #3	$172.63	8.220%	$186.8202	$186.82	$186.80	$186.80
Purchase #4	$191.86	13.580%	$217.9146	$217.91	$217.90	$217.90
Purchase #5	$33.91	9.546%	$37.147	$37.15	$37.15	$37.10
Purchase #6	$143.32	6.680%	$152.8938	$152.89	$152.90	$152.90
Purchase #7	$49.35	10.774%	$54.667	$54.67	$54.65	$54.70
7 purchase totals =	$849.95		$942.3846	$942.39	$942.35	$942.30