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	$223.26	8.359%	$241.9223	$241.92	$241.90	$241.90
Purchase #2	$213.95	4.807%	$224.2346	$224.23	$224.25	$224.20
Purchase #3	$65.77	10.870%	$72.9192	$72.92	$72.90	$72.90
Purchase #4	$129.43	11.164%	$143.8796	$143.88	$143.90	$143.90
Purchase #5	$133.54	7.677%	$143.7919	$143.79	$143.80	$143.80
Purchase #6	$8.58	5.549%	$9.0561	$9.06	$9.05	$9.10
Purchase #7	$224.67	11.680%	$250.9115	$250.91	$250.90	$250.90
7 purchase totals =	$999.20		$1,086.7152	$1,086.71	$1,086.70	$1,086.70