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	$61.71	12.193%	$69.2343	$69.23	$69.25	$69.20
Purchase #2	$11.43	13.554%	$12.9792	$12.98	$13.00	$13.00
Purchase #3	$159.37	6.696%	$170.0414	$170.04	$170.05	$170.00
Purchase #4	$65.92	10.559%	$72.8805	$72.88	$72.90	$72.90
Purchase #5	$123.31	6.138%	$130.8788	$130.88	$130.90	$130.90
Purchase #6	$141.75	4.329%	$147.8864	$147.89	$147.90	$147.90
Purchase #7	$237.38	4.847%	$248.8858	$248.89	$248.90	$248.90
7 purchase totals =	$800.87		$852.7864	$852.79	$852.90	$852.80