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	$66.38	3.800%	$68.9024	$68.90	$68.90	$68.90
Purchase #2	$55.82	3.547%	$57.7999	$57.80	$57.80	$57.80
Purchase #3	$178.33	8.842%	$194.0979	$194.10	$194.10	$194.10
Purchase #4	$126.28	4.241%	$131.6355	$131.64	$131.65	$131.60
Purchase #5	$117.98	11.439%	$131.4757	$131.48	$131.50	$131.50
Purchase #6	$173.98	12.423%	$195.5935	$195.59	$195.60	$195.60
Purchase #7	$6.70	11.153%	$7.4473	$7.45	$7.45	$7.40
7 purchase totals =	$725.47		$786.9522	$786.96	$787.00	$786.90