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	$13.32	5.717%	$14.0815	$14.08	$14.10	$14.10
Purchase #2	$111.34	11.712%	$124.3801	$124.38	$124.40	$124.40
Purchase #3	$102.33	11.324%	$113.9178	$113.92	$113.90	$113.90
Purchase #4	$40.59	3.724%	$42.1016	$42.10	$42.10	$42.10
Purchase #5	$89.66	9.175%	$97.8863	$97.89	$97.90	$97.90
Purchase #6	$28.70	11.512%	$32.0039	$32.00	$32.00	$32.00
Purchase #7	$112.83	11.134%	$125.3925	$125.39	$125.40	$125.40
7 purchase totals =	$498.77		$549.7637	$549.76	$549.80	$549.80