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	$87.31	4.811%	$91.5105	$91.51	$91.50	$91.50
Purchase #2	$42.78	8.165%	$46.273	$46.27	$46.25	$46.30
Purchase #3	$51.39	4.507%	$53.7061	$53.71	$53.70	$53.70
Purchase #4	$118.44	5.389%	$124.8227	$124.82	$124.80	$124.80
Purchase #5	$220.73	13.655%	$250.8707	$250.87	$250.85	$250.90
Purchase #6	$104.65	4.727%	$109.5968	$109.60	$109.60	$109.60
Purchase #7	$37.60	4.550%	$39.3108	$39.31	$39.30	$39.30
7 purchase totals =	$662.90		$716.0906	$716.09	$716.00	$716.10