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	$92.91	8.432%	$100.7442	$100.74	$100.75	$100.70
Purchase #2	$12.82	6.698%	$13.6787	$13.68	$13.70	$13.70
Purchase #3	$39.37	6.694%	$42.0054	$42.01	$42.00	$42.00
Purchase #4	$84.46	9.598%	$92.5665	$92.57	$92.55	$92.60
Purchase #5	$11.35	8.682%	$12.3354	$12.34	$12.35	$12.30
Purchase #6	$152.64	12.594%	$171.8635	$171.86	$171.85	$171.90
Purchase #7	$60.38	8.599%	$65.5721	$65.57	$65.55	$65.60
7 purchase totals =	$453.93		$498.7658	$498.77	$498.75	$498.80