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	$116.76	4.851%	$122.424	$122.42	$122.40	$122.40
Purchase #2	$27.45	7.305%	$29.4552	$29.46	$29.45	$29.50
Purchase #3	$75.58	4.405%	$78.9093	$78.91	$78.90	$78.90
Purchase #4	$25.44	8.432%	$27.5851	$27.59	$27.60	$27.60
Purchase #5	$135.83	6.253%	$144.3234	$144.32	$144.30	$144.30
Purchase #6	$131.37	7.203%	$140.8326	$140.83	$140.85	$140.80
Purchase #7	$125.50	12.300%	$140.9365	$140.94	$140.95	$140.90
7 purchase totals =	$637.93		$684.4661	$684.47	$684.45	$684.40