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	$181.31	8.380%	$196.5038	$196.50	$196.50	$196.50
Purchase #2	$58.52	7.516%	$62.9184	$62.92	$62.90	$62.90
Purchase #3	$199.91	11.292%	$222.4838	$222.48	$222.50	$222.50
Purchase #4	$85.47	5.578%	$90.2375	$90.24	$90.25	$90.20
Purchase #5	$235.82	12.357%	$264.9603	$264.96	$264.95	$265.00
Purchase #6	$40.37	5.821%	$42.7199	$42.72	$42.70	$42.70
Purchase #7	$226.90	9.659%	$248.8163	$248.82	$248.80	$248.80
7 purchase totals =	$1,028.30		$1,128.6400	$1,128.64	$1,128.60	$1,128.60