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	$99.76	4.102%	$103.8522	$103.85	$103.85	$103.90
Purchase #2	$42.83	7.536%	$46.0577	$46.06	$46.05	$46.10
Purchase #3	$40.84	12.772%	$46.0561	$46.06	$46.05	$46.10
Purchase #4	$147.94	12.671%	$166.6855	$166.69	$166.70	$166.70
Purchase #5	$99.39	12.822%	$112.1338	$112.13	$112.15	$112.10
Purchase #6	$38.45	7.827%	$41.4595	$41.46	$41.45	$41.50
Purchase #7	$176.43	4.863%	$185.0098	$185.01	$185.00	$185.00
7 purchase totals =	$645.64		$701.2546	$701.26	$701.25	$701.40