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	$88.86	10.123%	$97.8553	$97.86	$97.85	$97.90
Purchase #2	$103.77	5.825%	$109.8146	$109.81	$109.80	$109.80
Purchase #3	$173.47	12.111%	$194.479	$194.48	$194.50	$194.50
Purchase #4	$80.66	6.576%	$85.9642	$85.96	$85.95	$86.00
Purchase #5	$146.29	10.749%	$162.0147	$162.01	$162.00	$162.00
Purchase #6	$165.78	6.268%	$176.1711	$176.17	$176.15	$176.20
Purchase #7	$78.97	12.816%	$89.0908	$89.09	$89.10	$89.10
7 purchase totals =	$837.80		$915.3897	$915.38	$915.35	$915.50