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	$232.72	11.347%	$259.1267	$259.13	$259.15	$259.10
Purchase #2	$155.47	11.678%	$173.6258	$173.63	$173.65	$173.60
Purchase #3	$145.34	3.559%	$150.5127	$150.51	$150.50	$150.50
Purchase #4	$40.56	6.576%	$43.2272	$43.23	$43.25	$43.20
Purchase #5	$90.79	12.336%	$101.9899	$101.99	$102.00	$102.00
Purchase #6	$223.67	11.808%	$250.081	$250.08	$250.10	$250.10
Purchase #7	$63.32	13.269%	$71.7219	$71.72	$71.70	$71.70
7 purchase totals =	$951.87		$1,050.2852	$1,050.29	$1,050.35	$1,050.20