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	$224.78	12.825%	$253.608	$253.61	$253.60	$253.60
Purchase #2	$198.64	10.218%	$218.937	$218.94	$218.95	$218.90
Purchase #3	$83.47	10.840%	$92.5181	$92.52	$92.50	$92.50
Purchase #4	$129.49	11.313%	$144.1392	$144.14	$144.15	$144.10
Purchase #5	$165.46	3.680%	$171.5489	$171.55	$171.55	$171.50
Purchase #6	$67.65	12.136%	$75.86	$75.86	$75.85	$75.90
Purchase #7	$155.62	9.794%	$170.8614	$170.86	$170.85	$170.90
7 purchase totals =	$1,025.11		$1,127.4726	$1,127.48	$1,127.45	$1,127.40