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	$87.25	6.297%	$92.7441	$92.74	$92.75	$92.70
Purchase #2	$213.97	4.208%	$222.9739	$222.97	$222.95	$223.00
Purchase #3	$142.98	9.691%	$156.8362	$156.84	$156.85	$156.80
Purchase #4	$168.58	11.132%	$187.3463	$187.35	$187.35	$187.30
Purchase #5	$111.96	3.168%	$115.5069	$115.51	$115.50	$115.50
Purchase #6	$64.65	13.654%	$73.4773	$73.48	$73.50	$73.50
Purchase #7	$215.95	3.110%	$222.666	$222.67	$222.65	$222.70
7 purchase totals =	$1,005.34		$1,071.5507	$1,071.56	$1,071.55	$1,071.50