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	$55.49	11.549%	$61.8985	$61.90	$61.90	$61.90
Purchase #2	$71.87	8.638%	$78.0781	$78.08	$78.10	$78.10
Purchase #3	$31.84	5.661%	$33.6425	$33.64	$33.65	$33.60
Purchase #4	$90.76	13.527%	$103.0371	$103.04	$103.05	$103.00
Purchase #5	$118.31	6.383%	$125.8617	$125.86	$125.85	$125.90
Purchase #6	$60.47	6.717%	$64.5318	$64.53	$64.55	$64.50
Purchase #7	$139.49	9.717%	$153.0442	$153.04	$153.05	$153.00
7 purchase totals =	$568.23		$620.0939	$620.09	$620.15	$620.00