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	$160.48	9.595%	$175.8781	$175.88	$175.90	$175.90
Purchase #2	$221.59	11.219%	$246.4502	$246.45	$246.45	$246.50
Purchase #3	$91.39	4.370%	$95.3837	$95.38	$95.40	$95.40
Purchase #4	$111.52	13.585%	$126.67	$126.67	$126.65	$126.70
Purchase #5	$227.27	12.640%	$255.9969	$256.00	$256.00	$256.00
Purchase #6	$39.87	9.104%	$43.4998	$43.50	$43.50	$43.50
Purchase #7	$140.59	11.283%	$156.4528	$156.45	$156.45	$156.50
7 purchase totals =	$992.71		$1,100.3315	$1,100.33	$1,100.35	$1,100.50