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	$143.40	12.750%	$161.6835	$161.68	$161.70	$161.70
Purchase #2	$150.52	4.129%	$156.735	$156.74	$156.75	$156.70
Purchase #3	$200.92	5.107%	$211.181	$211.18	$211.20	$211.20
Purchase #4	$87.46	3.429%	$90.459	$90.46	$90.45	$90.50
Purchase #5	$186.86	12.538%	$210.2885	$210.29	$210.30	$210.30
Purchase #6	$76.88	6.719%	$82.0456	$82.05	$82.05	$82.00
Purchase #7	$170.66	10.452%	$188.4974	$188.50	$188.50	$188.50
7 purchase totals =	$1,016.70		$1,100.8900	$1,100.90	$1,100.95	$1,100.90