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	$230.32	11.207%	$256.132	$256.13	$256.15	$256.10
Purchase #2	$146.54	5.181%	$154.1322	$154.13	$154.15	$154.10
Purchase #3	$190.42	12.288%	$213.8188	$213.82	$213.80	$213.80
Purchase #4	$76.46	13.659%	$86.9037	$86.90	$86.90	$86.90
Purchase #5	$214.59	11.846%	$240.0103	$240.01	$240.00	$240.00
Purchase #6	$29.31	6.117%	$31.1029	$31.10	$31.10	$31.10
Purchase #7	$57.57	13.461%	$65.3195	$65.32	$65.30	$65.30
7 purchase totals =	$945.21		$1,047.4194	$1,047.41	$1,047.40	$1,047.30