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	$43.72	11.216%	$48.6236	$48.62	$48.60	$48.60
Purchase #2	$158.76	7.405%	$170.5162	$170.52	$170.50	$170.50
Purchase #3	$93.60	6.426%	$99.6147	$99.61	$99.60	$99.60
Purchase #4	$249.66	3.681%	$258.85	$258.85	$258.85	$258.90
Purchase #5	$138.98	13.523%	$157.7743	$157.77	$157.75	$157.80
Purchase #6	$66.52	9.560%	$72.8793	$72.88	$72.90	$72.90
Purchase #7	$49.39	7.345%	$53.0177	$53.02	$53.00	$53.00
7 purchase totals =	$800.63		$861.2758	$861.27	$861.20	$861.30