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	$241.72	10.583%	$267.3012	$267.30	$267.30	$267.30
Purchase #2	$64.70	11.568%	$72.1845	$72.18	$72.20	$72.20
Purchase #3	$198.78	6.737%	$212.1718	$212.17	$212.15	$212.20
Purchase #4	$52.54	12.328%	$59.0171	$59.02	$59.00	$59.00
Purchase #5	$134.47	9.164%	$146.7928	$146.79	$146.80	$146.80
Purchase #6	$121.81	4.703%	$127.5387	$127.54	$127.55	$127.50
Purchase #7	$71.56	3.297%	$73.9193	$73.92	$73.90	$73.90
7 purchase totals =	$885.58		$958.9254	$958.92	$958.90	$958.90