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	$211.56	9.260%	$231.1505	$231.15	$231.15	$231.20
Purchase #2	$95.53	9.622%	$104.7219	$104.72	$104.70	$104.70
Purchase #3	$141.93	13.331%	$160.8507	$160.85	$160.85	$160.90
Purchase #4	$156.91	9.697%	$172.1256	$172.13	$172.15	$172.10
Purchase #5	$85.34	8.239%	$92.3712	$92.37	$92.35	$92.40
Purchase #6	$137.70	6.524%	$146.6835	$146.68	$146.70	$146.70
Purchase #7	$178.96	5.590%	$188.9639	$188.96	$188.95	$189.00
7 purchase totals =	$1,007.93		$1,096.8673	$1,096.86	$1,096.85	$1,097.00