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	$207.75	5.761%	$219.7185	$219.72	$219.70	$219.70
Purchase #2	$50.48	6.729%	$53.8768	$53.88	$53.90	$53.90
Purchase #3	$161.29	8.519%	$175.0303	$175.03	$175.05	$175.00
Purchase #4	$218.38	10.174%	$240.598	$240.60	$240.60	$240.60
Purchase #5	$32.49	4.196%	$33.8533	$33.85	$33.85	$33.90
Purchase #6	$174.59	6.182%	$185.3832	$185.38	$185.40	$185.40
Purchase #7	$126.36	13.638%	$143.593	$143.59	$143.60	$143.60
7 purchase totals =	$971.34		$1,052.0531	$1,052.05	$1,052.10	$1,052.10