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	$124.48	9.813%	$136.6952	$136.70	$136.70	$136.70
Purchase #2	$140.58	6.766%	$150.0916	$150.09	$150.10	$150.10
Purchase #3	$136.48	3.819%	$141.6922	$141.69	$141.70	$141.70
Purchase #4	$228.56	7.330%	$245.3134	$245.31	$245.30	$245.30
Purchase #5	$76.45	11.847%	$85.507	$85.51	$85.50	$85.50
Purchase #6	$39.82	6.722%	$42.4967	$42.50	$42.50	$42.50
Purchase #7	$195.67	9.485%	$214.2293	$214.23	$214.25	$214.20
7 purchase totals =	$942.04		$1,016.0254	$1,016.03	$1,016.05	$1,016.00