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	$101.34	3.350%	$104.7349	$104.73	$104.75	$104.70
Purchase #2	$198.74	12.152%	$222.8909	$222.89	$222.90	$222.90
Purchase #3	$230.70	11.538%	$257.3182	$257.32	$257.30	$257.30
Purchase #4	$65.40	11.587%	$72.9779	$72.98	$73.00	$73.00
Purchase #5	$17.44	13.443%	$19.7845	$19.78	$19.80	$19.80
Purchase #6	$123.98	13.797%	$141.0855	$141.09	$141.10	$141.10
Purchase #7	$214.55	12.690%	$241.7764	$241.78	$241.80	$241.80
7 purchase totals =	$952.15		$1,060.5683	$1,060.57	$1,060.65	$1,060.60