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	$221.52	5.535%	$233.7811	$233.78	$233.80	$233.80
Purchase #2	$6.35	10.245%	$7.0006	$7.00	$7.00	$7.00
Purchase #3	$163.70	6.771%	$174.7841	$174.78	$174.80	$174.80
Purchase #4	$112.27	11.125%	$124.76	$124.76	$124.75	$124.80
Purchase #5	$216.70	10.137%	$238.6669	$238.67	$238.65	$238.70
Purchase #6	$133.99	12.119%	$150.2282	$150.23	$150.25	$150.20
Purchase #7	$72.76	12.794%	$82.0689	$82.07	$82.05	$82.10
7 purchase totals =	$927.29		$1,011.2898	$1,011.29	$1,011.30	$1,011.40