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	$74.69	9.812%	$82.0186	$82.02	$82.00	$82.00
Purchase #2	$83.44	13.141%	$94.4049	$94.40	$94.40	$94.40
Purchase #3	$115.25	7.149%	$123.4892	$123.49	$123.50	$123.50
Purchase #4	$193.57	4.377%	$202.0426	$202.04	$202.05	$202.00
Purchase #5	$247.98	7.783%	$267.2803	$267.28	$267.30	$267.30
Purchase #6	$56.77	5.579%	$59.9372	$59.94	$59.95	$59.90
Purchase #7	$27.53	13.627%	$31.2815	$31.28	$31.30	$31.30
7 purchase totals =	$799.23		$860.4543	$860.45	$860.50	$860.40