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	$195.26	10.699%	$216.1509	$216.15	$216.15	$216.20
Purchase #2	$60.87	8.268%	$65.9027	$65.90	$65.90	$65.90
Purchase #3	$139.35	4.111%	$145.0787	$145.08	$145.10	$145.10
Purchase #4	$61.63	7.624%	$66.3287	$66.33	$66.35	$66.30
Purchase #5	$249.26	11.861%	$278.8247	$278.82	$278.80	$278.80
Purchase #6	$45.42	11.554%	$50.6678	$50.67	$50.65	$50.70
Purchase #7	$105.70	3.428%	$109.3234	$109.32	$109.30	$109.30
7 purchase totals =	$857.49		$932.2769	$932.27	$932.25	$932.30