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	$63.92	4.415%	$66.7421	$66.74	$66.75	$66.70
Purchase #2	$157.92	10.741%	$174.8822	$174.88	$174.90	$174.90
Purchase #3	$94.48	7.773%	$101.8239	$101.82	$101.80	$101.80
Purchase #4	$187.32	4.596%	$195.9292	$195.93	$195.95	$195.90
Purchase #5	$134.61	5.360%	$141.8251	$141.83	$141.85	$141.80
Purchase #6	$176.72	10.351%	$195.0123	$195.01	$195.00	$195.00
Purchase #7	$200.55	11.158%	$222.9274	$222.93	$222.95	$222.90
7 purchase totals =	$1,015.52		$1,099.1422	$1,099.14	$1,099.20	$1,099.00