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	$175.40	12.250%	$196.8865	$196.89	$196.90	$196.90
Purchase #2	$227.66	7.609%	$244.9826	$244.98	$245.00	$245.00
Purchase #3	$34.51	13.287%	$39.0953	$39.10	$39.10	$39.10
Purchase #4	$108.71	6.771%	$116.0708	$116.07	$116.05	$116.10
Purchase #5	$234.99	4.730%	$246.105	$246.11	$246.10	$246.10
Purchase #6	$74.34	11.211%	$82.6743	$82.67	$82.65	$82.70
Purchase #7	$47.43	7.583%	$51.0266	$51.03	$51.05	$51.00
7 purchase totals =	$903.04		$976.8411	$976.85	$976.85	$976.90