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	$156.33	6.801%	$166.962	$166.96	$166.95	$167.00
Purchase #2	$91.83	9.347%	$100.4134	$100.41	$100.40	$100.40
Purchase #3	$247.98	5.490%	$261.5941	$261.59	$261.60	$261.60
Purchase #4	$88.46	12.820%	$99.8006	$99.80	$99.80	$99.80
Purchase #5	$94.73	9.535%	$103.7625	$103.76	$103.75	$103.80
Purchase #6	$205.30	4.725%	$215.0004	$215.00	$215.00	$215.00
Purchase #7	$25.63	8.746%	$27.8716	$27.87	$27.85	$27.90
7 purchase totals =	$910.26		$975.4046	$975.39	$975.35	$975.50