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	$203.78	10.591%	$225.3623	$225.36	$225.35	$225.40
Purchase #2	$177.80	13.540%	$201.8741	$201.87	$201.85	$201.90
Purchase #3	$39.97	8.499%	$43.3671	$43.37	$43.35	$43.40
Purchase #4	$81.36	11.753%	$90.9222	$90.92	$90.90	$90.90
Purchase #5	$219.63	13.831%	$250.007	$250.01	$250.00	$250.00
Purchase #6	$201.45	3.808%	$209.1212	$209.12	$209.10	$209.10
Purchase #7	$117.73	5.141%	$123.7825	$123.78	$123.80	$123.80
7 purchase totals =	$1,041.72		$1,144.4364	$1,144.43	$1,144.35	$1,144.50