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	$38.85	12.452%	$43.6876	$43.69	$43.70	$43.70
Purchase #2	$250.56	12.511%	$281.9076	$281.91	$281.90	$281.90
Purchase #3	$84.98	5.570%	$89.7134	$89.71	$89.70	$89.70
Purchase #4	$38.73	13.479%	$43.9504	$43.95	$43.95	$44.00
Purchase #5	$77.85	8.534%	$84.4937	$84.49	$84.50	$84.50
Purchase #6	$211.95	13.520%	$240.6056	$240.61	$240.60	$240.60
Purchase #7	$89.52	9.644%	$98.1533	$98.15	$98.15	$98.20
7 purchase totals =	$792.44		$882.5116	$882.51	$882.50	$882.60