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	$43.81	11.726%	$48.9472	$48.95	$48.95	$48.90
Purchase #2	$79.27	12.459%	$89.1462	$89.15	$89.15	$89.10
Purchase #3	$40.53	5.538%	$42.7746	$42.77	$42.75	$42.80
Purchase #4	$50.37	9.204%	$55.0061	$55.01	$55.00	$55.00
Purchase #5	$108.70	11.169%	$120.8407	$120.84	$120.85	$120.80
Purchase #6	$45.60	4.755%	$47.7683	$47.77	$47.75	$47.80
Purchase #7	$78.43	10.616%	$86.7561	$86.76	$86.75	$86.80
7 purchase totals =	$446.71		$491.2392	$491.25	$491.20	$491.20