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	$133.92	10.747%	$148.3124	$148.31	$148.30	$148.30
Purchase #2	$72.97	5.483%	$76.9709	$76.97	$76.95	$77.00
Purchase #3	$48.30	8.772%	$52.5369	$52.54	$52.55	$52.50
Purchase #4	$135.40	6.606%	$144.3445	$144.34	$144.35	$144.30
Purchase #5	$45.59	3.597%	$47.2299	$47.23	$47.25	$47.20
Purchase #6	$130.28	10.391%	$143.8174	$143.82	$143.80	$143.80
Purchase #7	$133.92	6.202%	$142.2257	$142.23	$142.25	$142.20
7 purchase totals =	$700.38		$755.4377	$755.44	$755.45	$755.30