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	$188.25	12.806%	$212.3573	$212.36	$212.35	$212.40
Purchase #2	$58.91	10.627%	$65.1704	$65.17	$65.15	$65.20
Purchase #3	$160.85	12.348%	$180.7118	$180.71	$180.70	$180.70
Purchase #4	$168.45	12.723%	$189.8819	$189.88	$189.90	$189.90
Purchase #5	$153.25	3.452%	$158.5402	$158.54	$158.55	$158.50
Purchase #6	$148.71	7.441%	$159.7755	$159.78	$159.80	$159.80
Purchase #7	$190.59	4.712%	$199.5706	$199.57	$199.55	$199.60
7 purchase totals =	$1,069.01		$1,166.0077	$1,166.01	$1,166.00	$1,166.10