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	$47.83	10.160%	$52.6895	$52.69	$52.70	$52.70
Purchase #2	$74.47	11.351%	$82.9231	$82.92	$82.90	$82.90
Purchase #3	$208.69	6.224%	$221.6789	$221.68	$221.70	$221.70
Purchase #4	$33.66	10.525%	$37.2027	$37.20	$37.20	$37.20
Purchase #5	$153.89	9.645%	$168.7327	$168.73	$168.75	$168.70
Purchase #6	$210.92	10.782%	$233.6614	$233.66	$233.65	$233.70
Purchase #7	$228.81	5.565%	$241.5433	$241.54	$241.55	$241.50
7 purchase totals =	$958.27		$1,038.4316	$1,038.42	$1,038.45	$1,038.40