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	$89.36	3.580%	$92.5591	$92.56	$92.55	$92.60
Purchase #2	$132.57	5.185%	$139.4438	$139.44	$139.45	$139.40
Purchase #3	$18.45	5.404%	$19.447	$19.45	$19.45	$19.40
Purchase #4	$154.95	9.229%	$169.2503	$169.25	$169.25	$169.30
Purchase #5	$71.81	7.122%	$76.9243	$76.92	$76.90	$76.90
Purchase #6	$28.44	12.457%	$31.9828	$31.98	$32.00	$32.00
Purchase #7	$37.52	8.646%	$40.764	$40.76	$40.75	$40.80
7 purchase totals =	$533.10		$570.3713	$570.36	$570.35	$570.40