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	$155.99	5.340%	$164.3199	$164.32	$164.30	$164.30
Purchase #2	$88.32	12.817%	$99.64	$99.64	$99.65	$99.60
Purchase #3	$172.76	3.653%	$179.0709	$179.07	$179.05	$179.10
Purchase #4	$29.46	10.535%	$32.5636	$32.56	$32.55	$32.60
Purchase #5	$119.71	12.678%	$134.8868	$134.89	$134.90	$134.90
Purchase #6	$226.88	6.824%	$242.3623	$242.36	$242.35	$242.40
Purchase #7	$221.59	11.351%	$246.7427	$246.74	$246.75	$246.70
7 purchase totals =	$1,014.71		$1,099.5862	$1,099.58	$1,099.55	$1,099.60