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	$227.89	5.507%	$240.4399	$240.44	$240.45	$240.40
Purchase #2	$233.38	6.172%	$247.7842	$247.78	$247.80	$247.80
Purchase #3	$109.45	3.266%	$113.0246	$113.02	$113.00	$113.00
Purchase #4	$31.56	9.270%	$34.4856	$34.49	$34.50	$34.50
Purchase #5	$39.98	12.790%	$45.0934	$45.09	$45.10	$45.10
Purchase #6	$40.48	12.861%	$45.6861	$45.69	$45.70	$45.70
Purchase #7	$87.91	11.388%	$97.9212	$97.92	$97.90	$97.90
7 purchase totals =	$770.65		$824.4350	$824.43	$824.45	$824.40