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	$185.49	10.290%	$204.5769	$204.58	$204.60	$204.60
Purchase #2	$64.91	13.750%	$73.8351	$73.84	$73.85	$73.80
Purchase #3	$89.52	11.849%	$100.1272	$100.13	$100.15	$100.10
Purchase #4	$92.56	10.830%	$102.5842	$102.58	$102.60	$102.60
Purchase #5	$244.87	3.547%	$253.5555	$253.56	$253.55	$253.60
Purchase #6	$38.51	8.831%	$41.9108	$41.91	$41.90	$41.90
Purchase #7	$211.25	9.508%	$231.3357	$231.34	$231.35	$231.30
7 purchase totals =	$927.11		$1,007.9254	$1,007.94	$1,008.00	$1,007.90