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	$175.64	3.364%	$181.5485	$181.55	$181.55	$181.50
Purchase #2	$172.68	10.733%	$191.2137	$191.21	$191.20	$191.20
Purchase #3	$78.61	12.635%	$88.5424	$88.54	$88.55	$88.50
Purchase #4	$219.57	12.324%	$246.6298	$246.63	$246.65	$246.60
Purchase #5	$209.91	12.368%	$235.8717	$235.87	$235.85	$235.90
Purchase #6	$91.61	10.393%	$101.131	$101.13	$101.15	$101.10
Purchase #7	$95.72	10.548%	$105.8165	$105.82	$105.80	$105.80
7 purchase totals =	$1,043.74		$1,150.7536	$1,150.75	$1,150.75	$1,150.60