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	$132.62	10.412%	$146.4284	$146.43	$146.45	$146.40
Purchase #2	$181.79	13.281%	$205.9335	$205.93	$205.95	$205.90
Purchase #3	$222.66	13.854%	$253.5073	$253.51	$253.50	$253.50
Purchase #4	$206.41	9.584%	$226.1923	$226.19	$226.20	$226.20
Purchase #5	$106.98	9.799%	$117.463	$117.46	$117.45	$117.50
Purchase #6	$97.69	5.672%	$103.231	$103.23	$103.25	$103.20
Purchase #7	$175.63	5.546%	$185.3704	$185.37	$185.35	$185.40
7 purchase totals =	$1,123.78		$1,238.1259	$1,238.12	$1,238.15	$1,238.10