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	$108.95	8.266%	$117.9558	$117.96	$117.95	$118.00
Purchase #2	$176.43	11.318%	$196.3983	$196.40	$196.40	$196.40
Purchase #3	$5.56	12.593%	$6.2602	$6.26	$6.25	$6.30
Purchase #4	$88.42	3.503%	$91.5174	$91.52	$91.50	$91.50
Purchase #5	$82.61	3.324%	$85.356	$85.36	$85.35	$85.40
Purchase #6	$114.89	3.132%	$118.4884	$118.49	$118.50	$118.50
Purchase #7	$165.57	5.660%	$174.9413	$174.94	$174.95	$174.90
7 purchase totals =	$742.43		$790.9174	$790.93	$790.90	$791.00