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	$64.67	12.163%	$72.5358	$72.54	$72.55	$72.50
Purchase #2	$73.87	3.528%	$76.4761	$76.48	$76.50	$76.50
Purchase #3	$205.58	3.473%	$212.7198	$212.72	$212.70	$212.70
Purchase #4	$143.61	11.385%	$159.96	$159.96	$159.95	$160.00
Purchase #5	$114.99	9.601%	$126.0302	$126.03	$126.05	$126.00
Purchase #6	$80.63	12.270%	$90.5233	$90.52	$90.50	$90.50
Purchase #7	$215.80	3.722%	$223.8321	$223.83	$223.85	$223.80
7 purchase totals =	$899.15		$962.0773	$962.08	$962.10	$962.00