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	$62.97	10.569%	$69.6253	$69.63	$69.65	$69.60
Purchase #2	$36.58	11.601%	$40.8236	$40.82	$40.80	$40.80
Purchase #3	$81.87	4.316%	$85.4035	$85.40	$85.40	$85.40
Purchase #4	$243.30	10.256%	$268.2528	$268.25	$268.25	$268.30
Purchase #5	$97.94	13.340%	$111.0052	$111.01	$111.00	$111.00
Purchase #6	$233.38	6.766%	$249.1705	$249.17	$249.15	$249.20
Purchase #7	$101.99	7.161%	$109.2935	$109.29	$109.30	$109.30
7 purchase totals =	$858.03		$933.5744	$933.57	$933.55	$933.60