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	$59.70	9.510%	$65.3775	$65.38	$65.40	$65.40
Purchase #2	$233.31	8.635%	$253.4563	$253.46	$253.45	$253.50
Purchase #3	$104.83	7.374%	$112.5602	$112.56	$112.55	$112.60
Purchase #4	$94.89	12.219%	$106.4846	$106.48	$106.50	$106.50
Purchase #5	$191.58	10.580%	$211.8492	$211.85	$211.85	$211.80
Purchase #6	$146.41	6.661%	$156.1624	$156.16	$156.15	$156.20
Purchase #7	$56.29	12.387%	$63.2626	$63.26	$63.25	$63.30
7 purchase totals =	$887.01		$969.1528	$969.15	$969.15	$969.30