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	$75.74	12.630%	$85.306	$85.31	$85.30	$85.30
Purchase #2	$9.55	11.512%	$10.6494	$10.65	$10.65	$10.60
Purchase #3	$92.79	7.781%	$100.01	$100.01	$100.00	$100.00
Purchase #4	$68.69	12.324%	$77.1554	$77.16	$77.15	$77.20
Purchase #5	$133.40	4.595%	$139.5297	$139.53	$139.55	$139.50
Purchase #6	$63.25	12.795%	$71.3428	$71.34	$71.35	$71.30
Purchase #7	$118.63	4.168%	$123.5745	$123.57	$123.55	$123.60
7 purchase totals =	$562.05		$607.5678	$607.57	$607.55	$607.50