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	$79.89	7.291%	$85.7148	$85.71	$85.70	$85.70
Purchase #2	$64.96	12.145%	$72.8494	$72.85	$72.85	$72.80
Purchase #3	$76.36	12.422%	$85.8454	$85.85	$85.85	$85.80
Purchase #4	$240.60	5.602%	$254.0784	$254.08	$254.10	$254.10
Purchase #5	$62.39	13.310%	$70.6941	$70.69	$70.70	$70.70
Purchase #6	$187.29	4.236%	$195.2236	$195.22	$195.20	$195.20
Purchase #7	$40.47	6.505%	$43.1026	$43.10	$43.10	$43.10
7 purchase totals =	$751.96		$807.5083	$807.50	$807.50	$807.40