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	$79.86	6.870%	$85.3464	$85.35	$85.35	$85.30
Purchase #2	$165.46	4.735%	$173.2945	$173.29	$173.30	$173.30
Purchase #3	$93.42	10.655%	$103.3739	$103.37	$103.35	$103.40
Purchase #4	$233.98	10.695%	$259.0042	$259.00	$259.00	$259.00
Purchase #5	$34.74	8.301%	$37.6238	$37.62	$37.60	$37.60
Purchase #6	$187.89	13.256%	$212.7967	$212.80	$212.80	$212.80
Purchase #7	$139.36	8.125%	$150.683	$150.68	$150.70	$150.70
7 purchase totals =	$934.71		$1,022.1225	$1,022.11	$1,022.10	$1,022.10