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	$86.52	7.455%	$92.9701	$92.97	$92.95	$93.00
Purchase #2	$211.37	6.742%	$225.6206	$225.62	$225.60	$225.60
Purchase #3	$246.48	11.402%	$274.5836	$274.58	$274.60	$274.60
Purchase #4	$201.83	10.381%	$222.782	$222.78	$222.80	$222.80
Purchase #5	$250.82	5.171%	$263.7899	$263.79	$263.80	$263.80
Purchase #6	$52.57	12.291%	$59.0314	$59.03	$59.05	$59.00
Purchase #7	$90.46	9.564%	$99.1116	$99.11	$99.10	$99.10
7 purchase totals =	$1,140.05		$1,237.8892	$1,237.88	$1,237.90	$1,237.90