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	$81.94	4.407%	$85.5511	$85.55	$85.55	$85.60
Purchase #2	$66.63	3.161%	$68.7362	$68.74	$68.75	$68.70
Purchase #3	$97.25	8.634%	$105.6466	$105.65	$105.65	$105.60
Purchase #4	$210.84	8.319%	$228.3798	$228.38	$228.40	$228.40
Purchase #5	$110.96	12.750%	$125.1074	$125.11	$125.10	$125.10
Purchase #6	$72.89	8.308%	$78.9457	$78.95	$78.95	$78.90
Purchase #7	$151.67	11.103%	$168.5099	$168.51	$168.50	$168.50
7 purchase totals =	$792.18		$860.8767	$860.89	$860.90	$860.80