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	$99.53	3.637%	$103.1499	$103.15	$103.15	$103.10
Purchase #2	$143.43	13.387%	$162.631	$162.63	$162.65	$162.60
Purchase #3	$105.26	8.478%	$114.1839	$114.18	$114.20	$114.20
Purchase #4	$215.85	12.704%	$243.2716	$243.27	$243.25	$243.30
Purchase #5	$28.64	10.391%	$31.616	$31.62	$31.60	$31.60
Purchase #6	$232.34	9.736%	$254.9606	$254.96	$254.95	$255.00
Purchase #7	$199.36	12.105%	$223.4925	$223.49	$223.50	$223.50
7 purchase totals =	$1,024.41		$1,133.3055	$1,133.30	$1,133.30	$1,133.30