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	$95.30	11.594%	$106.3491	$106.35	$106.35	$106.30
Purchase #2	$78.85	8.169%	$85.2913	$85.29	$85.30	$85.30
Purchase #3	$232.98	13.618%	$264.7072	$264.71	$264.70	$264.70
Purchase #4	$63.94	7.680%	$68.8506	$68.85	$68.85	$68.90
Purchase #5	$243.60	4.714%	$255.0833	$255.08	$255.10	$255.10
Purchase #6	$235.32	6.508%	$250.6346	$250.63	$250.65	$250.60
Purchase #7	$45.39	12.518%	$51.0719	$51.07	$51.05	$51.10
7 purchase totals =	$995.38		$1,081.9880	$1,081.98	$1,082.00	$1,082.00