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	$43.59	3.599%	$45.1588	$45.16	$45.15	$45.20
Purchase #2	$148.85	3.192%	$153.6013	$153.60	$153.60	$153.60
Purchase #3	$138.43	5.870%	$146.5558	$146.56	$146.55	$146.60
Purchase #4	$86.61	5.122%	$91.0462	$91.05	$91.05	$91.00
Purchase #5	$90.75	9.452%	$99.3277	$99.33	$99.35	$99.30
Purchase #6	$237.37	3.313%	$245.2341	$245.23	$245.25	$245.20
Purchase #7	$142.50	7.590%	$153.3158	$153.32	$153.30	$153.30
7 purchase totals =	$888.10		$934.2397	$934.25	$934.25	$934.20