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	$207.40	4.856%	$217.4713	$217.47	$217.45	$217.50
Purchase #2	$184.69	6.309%	$196.3421	$196.34	$196.35	$196.30
Purchase #3	$175.83	8.399%	$190.598	$190.60	$190.60	$190.60
Purchase #4	$77.35	6.761%	$82.5796	$82.58	$82.60	$82.60
Purchase #5	$240.64	7.400%	$258.4474	$258.45	$258.45	$258.40
Purchase #6	$171.88	8.862%	$187.112	$187.11	$187.10	$187.10
Purchase #7	$250.67	5.347%	$264.0733	$264.07	$264.05	$264.10
7 purchase totals =	$1,308.46		$1,396.6237	$1,396.62	$1,396.60	$1,396.60