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	$93.97	5.403%	$99.0472	$99.05	$99.05	$99.00
Purchase #2	$24.56	3.196%	$25.3449	$25.34	$25.35	$25.30
Purchase #3	$104.86	6.198%	$111.3592	$111.36	$111.35	$111.40
Purchase #4	$69.58	3.254%	$71.8441	$71.84	$71.85	$71.80
Purchase #5	$39.94	3.512%	$41.3427	$41.34	$41.35	$41.30
Purchase #6	$164.43	8.163%	$177.8524	$177.85	$177.85	$177.90
Purchase #7	$165.27	7.759%	$178.0933	$178.09	$178.10	$178.10
7 purchase totals =	$662.61		$704.8838	$704.87	$704.90	$704.80