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	$105.87	13.181%	$119.8247	$119.82	$119.80	$119.80
Purchase #2	$233.96	3.603%	$242.3896	$242.39	$242.40	$242.40
Purchase #3	$135.54	3.307%	$140.0223	$140.02	$140.00	$140.00
Purchase #4	$118.26	6.497%	$125.9434	$125.94	$125.95	$125.90
Purchase #5	$125.94	13.724%	$143.224	$143.22	$143.20	$143.20
Purchase #6	$114.66	7.757%	$123.5542	$123.55	$123.55	$123.60
Purchase #7	$158.46	6.251%	$168.3653	$168.37	$168.35	$168.40
7 purchase totals =	$992.69		$1,063.3235	$1,063.31	$1,063.25	$1,063.30