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	$46.81	13.846%	$53.2913	$53.29	$53.30	$53.30
Purchase #2	$36.94	5.174%	$38.8513	$38.85	$38.85	$38.90
Purchase #3	$7.96	5.429%	$8.3921	$8.39	$8.40	$8.40
Purchase #4	$168.47	4.751%	$176.474	$176.47	$176.45	$176.50
Purchase #5	$106.71	5.805%	$112.9045	$112.90	$112.90	$112.90
Purchase #6	$54.34	13.401%	$61.6221	$61.62	$61.60	$61.60
Purchase #7	$57.40	6.291%	$61.011	$61.01	$61.00	$61.00
7 purchase totals =	$478.63		$512.5463	$512.53	$512.50	$512.60