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	$147.56	7.377%	$158.4455	$158.45	$158.45	$158.40
Purchase #2	$137.29	12.873%	$154.9633	$154.96	$154.95	$155.00
Purchase #3	$19.84	3.360%	$20.5066	$20.51	$20.50	$20.50
Purchase #4	$217.61	10.114%	$239.6191	$239.62	$239.60	$239.60
Purchase #5	$148.28	9.262%	$162.0137	$162.01	$162.00	$162.00
Purchase #6	$50.48	11.765%	$56.419	$56.42	$56.40	$56.40
Purchase #7	$202.46	11.313%	$225.3643	$225.36	$225.35	$225.40
7 purchase totals =	$923.52		$1,017.3315	$1,017.33	$1,017.25	$1,017.30