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	$196.73	9.519%	$215.4567	$215.46	$215.45	$215.50
Purchase #2	$227.75	12.515%	$256.2529	$256.25	$256.25	$256.30
Purchase #3	$52.86	5.469%	$55.7509	$55.75	$55.75	$55.80
Purchase #4	$220.89	4.537%	$230.9118	$230.91	$230.90	$230.90
Purchase #5	$30.61	5.205%	$32.2033	$32.20	$32.20	$32.20
Purchase #6	$30.39	4.729%	$31.8271	$31.83	$31.85	$31.80
Purchase #7	$210.64	11.451%	$234.7604	$234.76	$234.75	$234.80
7 purchase totals =	$969.87		$1,057.1631	$1,057.16	$1,057.15	$1,057.30