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	$196.76	6.156%	$208.8725	$208.87	$208.85	$208.90
Purchase #2	$35.57	4.675%	$37.2329	$37.23	$37.25	$37.20
Purchase #3	$199.43	12.270%	$223.9001	$223.90	$223.90	$223.90
Purchase #4	$27.94	11.138%	$31.052	$31.05	$31.05	$31.10
Purchase #5	$156.92	3.409%	$162.2694	$162.27	$162.25	$162.30
Purchase #6	$99.29	5.159%	$104.4124	$104.41	$104.40	$104.40
Purchase #7	$8.51	10.577%	$9.4101	$9.41	$9.40	$9.40
7 purchase totals =	$724.42		$777.1494	$777.14	$777.10	$777.20