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	$208.53	6.669%	$222.4369	$222.44	$222.45	$222.40
Purchase #2	$10.35	4.297%	$10.7947	$10.79	$10.80	$10.80
Purchase #3	$128.67	11.806%	$143.8608	$143.86	$143.85	$143.90
Purchase #4	$239.43	10.284%	$264.053	$264.05	$264.05	$264.10
Purchase #5	$28.99	11.791%	$32.4082	$32.41	$32.40	$32.40
Purchase #6	$11.55	13.450%	$13.1035	$13.10	$13.10	$13.10
Purchase #7	$160.27	11.824%	$179.2203	$179.22	$179.20	$179.20
7 purchase totals =	$787.79		$865.8774	$865.87	$865.85	$865.90