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	$128.72	9.822%	$141.3629	$141.36	$141.35	$141.40
Purchase #2	$227.55	12.535%	$256.0734	$256.07	$256.05	$256.10
Purchase #3	$101.58	3.575%	$105.2115	$105.21	$105.20	$105.20
Purchase #4	$24.74	9.644%	$27.1259	$27.13	$27.15	$27.10
Purchase #5	$21.89	11.195%	$24.3406	$24.34	$24.35	$24.30
Purchase #6	$63.76	3.346%	$65.8934	$65.89	$65.90	$65.90
Purchase #7	$100.83	11.691%	$112.618	$112.62	$112.60	$112.60
7 purchase totals =	$669.07		$732.6257	$732.62	$732.60	$732.60