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	$118.72	10.223%	$130.8567	$130.86	$130.85	$130.90
Purchase #2	$39.39	3.140%	$40.6268	$40.63	$40.65	$40.60
Purchase #3	$145.31	7.236%	$155.8246	$155.82	$155.80	$155.80
Purchase #4	$115.78	10.539%	$127.9821	$127.98	$128.00	$128.00
Purchase #5	$239.29	7.175%	$256.4591	$256.46	$256.45	$256.50
Purchase #6	$209.70	10.765%	$232.2742	$232.27	$232.25	$232.30
Purchase #7	$122.48	12.788%	$138.1427	$138.14	$138.15	$138.10
7 purchase totals =	$990.67		$1,082.1662	$1,082.16	$1,082.15	$1,082.20