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	$93.85	10.623%	$103.8197	$103.82	$103.80	$103.80
Purchase #2	$80.80	10.140%	$88.9931	$88.99	$89.00	$89.00
Purchase #3	$95.72	6.378%	$101.825	$101.83	$101.85	$101.80
Purchase #4	$64.77	10.562%	$71.611	$71.61	$71.60	$71.60
Purchase #5	$172.30	13.742%	$195.9775	$195.98	$196.00	$196.00
Purchase #6	$231.27	5.198%	$243.2914	$243.29	$243.30	$243.30
Purchase #7	$160.65	10.712%	$177.8588	$177.86	$177.85	$177.90
7 purchase totals =	$899.36		$983.3765	$983.38	$983.40	$983.40