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	$60.96	6.360%	$64.8371	$64.84	$64.85	$64.80
Purchase #2	$228.88	8.163%	$247.5635	$247.56	$247.55	$247.60
Purchase #3	$72.39	13.845%	$82.4124	$82.41	$82.40	$82.40
Purchase #4	$160.49	6.694%	$171.2332	$171.23	$171.25	$171.20
Purchase #5	$43.72	6.365%	$46.5028	$46.50	$46.50	$46.50
Purchase #6	$154.45	13.714%	$175.6313	$175.63	$175.65	$175.60
Purchase #7	$78.64	6.351%	$83.6344	$83.63	$83.65	$83.60
7 purchase totals =	$799.53		$871.8147	$871.80	$871.85	$871.70