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	$41.67	3.757%	$43.2355	$43.24	$43.25	$43.20
Purchase #2	$129.51	11.536%	$144.4503	$144.45	$144.45	$144.50
Purchase #3	$204.67	8.590%	$222.2512	$222.25	$222.25	$222.30
Purchase #4	$157.44	4.501%	$164.5264	$164.53	$164.55	$164.50
Purchase #5	$106.52	3.357%	$110.0959	$110.10	$110.10	$110.10
Purchase #6	$78.26	9.752%	$85.8919	$85.89	$85.90	$85.90
Purchase #7	$232.42	12.596%	$261.6956	$261.70	$261.70	$261.70
7 purchase totals =	$950.49		$1,032.1468	$1,032.16	$1,032.20	$1,032.20