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	$119.42	5.422%	$125.895	$125.90	$125.90	$125.90
Purchase #2	$233.37	7.356%	$250.5367	$250.54	$250.55	$250.50
Purchase #3	$76.53	9.566%	$83.8509	$83.85	$83.85	$83.90
Purchase #4	$85.53	9.768%	$93.8846	$93.88	$93.90	$93.90
Purchase #5	$222.39	5.163%	$233.872	$233.87	$233.85	$233.90
Purchase #6	$46.63	11.672%	$52.0727	$52.07	$52.05	$52.10
Purchase #7	$42.86	5.743%	$45.3214	$45.32	$45.30	$45.30
7 purchase totals =	$826.73		$885.4333	$885.43	$885.40	$885.50