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	$63.81	12.667%	$71.8928	$71.89	$71.90	$71.90
Purchase #2	$216.80	8.258%	$234.7033	$234.70	$234.70	$234.70
Purchase #3	$168.32	8.561%	$182.7299	$182.73	$182.75	$182.70
Purchase #4	$126.91	10.221%	$139.8815	$139.88	$139.90	$139.90
Purchase #5	$161.50	12.643%	$181.9184	$181.92	$181.90	$181.90
Purchase #6	$160.50	13.780%	$182.6169	$182.62	$182.60	$182.60
Purchase #7	$55.53	5.362%	$58.5075	$58.51	$58.50	$58.50
7 purchase totals =	$953.37		$1,052.2503	$1,052.25	$1,052.25	$1,052.20