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	$94.58	7.473%	$101.648	$101.65	$101.65	$101.60
Purchase #2	$54.53	5.574%	$57.5695	$57.57	$57.55	$57.60
Purchase #3	$146.43	3.323%	$151.2959	$151.30	$151.30	$151.30
Purchase #4	$31.80	6.222%	$33.7786	$33.78	$33.80	$33.80
Purchase #5	$108.63	3.624%	$112.5668	$112.57	$112.55	$112.60
Purchase #6	$134.83	11.855%	$150.8141	$150.81	$150.80	$150.80
Purchase #7	$46.37	4.754%	$48.5744	$48.57	$48.55	$48.60
7 purchase totals =	$617.17		$656.2473	$656.25	$656.20	$656.30