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	$151.30	13.762%	$172.1219	$172.12	$172.10	$172.10
Purchase #2	$209.69	13.398%	$237.7843	$237.78	$237.80	$237.80
Purchase #3	$87.74	8.480%	$95.1804	$95.18	$95.20	$95.20
Purchase #4	$183.62	9.161%	$200.4414	$200.44	$200.45	$200.40
Purchase #5	$31.94	3.141%	$32.9432	$32.94	$32.95	$32.90
Purchase #6	$69.52	3.738%	$72.1187	$72.12	$72.10	$72.10
Purchase #7	$141.58	6.184%	$150.3353	$150.34	$150.35	$150.30
7 purchase totals =	$875.39		$960.9252	$960.92	$960.95	$960.80