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	$49.25	5.727%	$52.0705	$52.07	$52.05	$52.10
Purchase #2	$59.27	11.218%	$65.9189	$65.92	$65.90	$65.90
Purchase #3	$238.94	7.528%	$256.9274	$256.93	$256.95	$256.90
Purchase #4	$49.67	4.776%	$52.0422	$52.04	$52.05	$52.00
Purchase #5	$213.29	6.546%	$227.252	$227.25	$227.25	$227.30
Purchase #6	$55.48	7.794%	$59.8041	$59.80	$59.80	$59.80
Purchase #7	$20.26	13.388%	$22.9724	$22.97	$22.95	$23.00
7 purchase totals =	$686.16		$736.9875	$736.98	$736.95	$737.00