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	$112.56	12.162%	$126.2495	$126.25	$126.25	$126.20
Purchase #2	$71.66	9.532%	$78.4906	$78.49	$78.50	$78.50
Purchase #3	$59.97	9.475%	$65.6522	$65.65	$65.65	$65.70
Purchase #4	$248.37	6.496%	$264.5041	$264.50	$264.50	$264.50
Purchase #5	$119.61	12.715%	$134.8184	$134.82	$134.80	$134.80
Purchase #6	$49.25	9.527%	$53.942	$53.94	$53.95	$53.90
Purchase #7	$220.63	5.478%	$232.7161	$232.72	$232.70	$232.70
7 purchase totals =	$882.05		$956.3729	$956.37	$956.35	$956.30