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	$41.35	10.870%	$45.8447	$45.84	$45.85	$45.80
Purchase #2	$69.94	6.612%	$74.5644	$74.56	$74.55	$74.60
Purchase #3	$94.48	5.524%	$99.6991	$99.70	$99.70	$99.70
Purchase #4	$161.58	4.145%	$168.2775	$168.28	$168.30	$168.30
Purchase #5	$80.57	7.335%	$86.4798	$86.48	$86.50	$86.50
Purchase #6	$37.54	11.838%	$41.984	$41.98	$42.00	$42.00
Purchase #7	$220.53	3.786%	$228.8793	$228.88	$228.90	$228.90
7 purchase totals =	$705.99		$745.7288	$745.72	$745.80	$745.80