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	$240.62	8.477%	$261.0174	$261.02	$261.00	$261.00
Purchase #2	$241.43	8.163%	$261.1379	$261.14	$261.15	$261.10
Purchase #3	$91.48	4.603%	$95.6908	$95.69	$95.70	$95.70
Purchase #4	$218.70	11.334%	$243.4875	$243.49	$243.50	$243.50
Purchase #5	$228.86	4.353%	$238.8223	$238.82	$238.80	$238.80
Purchase #6	$138.37	8.700%	$150.4082	$150.41	$150.40	$150.40
Purchase #7	$139.66	8.325%	$151.2867	$151.29	$151.30	$151.30
7 purchase totals =	$1,299.12		$1,401.8508	$1,401.86	$1,401.85	$1,401.80