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	$70.93	10.400%	$78.3067	$78.31	$78.30	$78.30
Purchase #2	$33.29	11.125%	$36.9935	$36.99	$37.00	$37.00
Purchase #3	$171.91	5.178%	$180.8115	$180.81	$180.80	$180.80
Purchase #4	$101.37	3.850%	$105.2727	$105.27	$105.25	$105.30
Purchase #5	$63.99	8.258%	$69.2743	$69.27	$69.25	$69.30
Purchase #6	$12.86	3.380%	$13.2947	$13.29	$13.30	$13.30
Purchase #7	$214.89	6.871%	$229.6551	$229.66	$229.65	$229.70
7 purchase totals =	$669.24		$713.6085	$713.60	$713.55	$713.70