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	$210.64	10.650%	$233.0732	$233.07	$233.05	$233.10
Purchase #2	$39.84	11.270%	$44.33	$44.33	$44.35	$44.30
Purchase #3	$170.80	12.699%	$192.4899	$192.49	$192.50	$192.50
Purchase #4	$18.72	8.546%	$20.3198	$20.32	$20.30	$20.30
Purchase #5	$90.83	9.695%	$99.636	$99.64	$99.65	$99.60
Purchase #6	$99.57	9.766%	$109.294	$109.29	$109.30	$109.30
Purchase #7	$230.94	11.304%	$257.0455	$257.05	$257.05	$257.00
7 purchase totals =	$861.34		$956.1884	$956.19	$956.20	$956.10