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	$242.64	5.375%	$255.6819	$255.68	$255.70	$255.70
Purchase #2	$81.28	5.607%	$85.8374	$85.84	$85.85	$85.80
Purchase #3	$100.44	8.554%	$109.0316	$109.03	$109.05	$109.00
Purchase #4	$221.56	8.327%	$240.0093	$240.01	$240.00	$240.00
Purchase #5	$196.34	10.840%	$217.6233	$217.62	$217.60	$217.60
Purchase #6	$200.75	11.344%	$223.5231	$223.52	$223.50	$223.50
Purchase #7	$45.38	8.471%	$49.2241	$49.22	$49.20	$49.20
7 purchase totals =	$1,088.39		$1,180.9307	$1,180.92	$1,180.90	$1,180.80