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	$134.83	4.517%	$140.9203	$140.92	$140.90	$140.90
Purchase #2	$239.43	4.728%	$250.7503	$250.75	$250.75	$250.80
Purchase #3	$99.35	13.645%	$112.9063	$112.91	$112.90	$112.90
Purchase #4	$81.84	4.741%	$85.72	$85.72	$85.70	$85.70
Purchase #5	$177.77	8.344%	$192.6031	$192.60	$192.60	$192.60
Purchase #6	$119.46	4.569%	$124.9181	$124.92	$124.90	$124.90
Purchase #7	$95.32	11.148%	$105.9463	$105.95	$105.95	$105.90
7 purchase totals =	$948.00		$1,013.7644	$1,013.77	$1,013.70	$1,013.70