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	$206.94	4.800%	$216.8731	$216.87	$216.85	$216.90
Purchase #2	$99.96	5.664%	$105.6217	$105.62	$105.60	$105.60
Purchase #3	$111.55	7.153%	$119.5292	$119.53	$119.55	$119.50
Purchase #4	$89.90	10.866%	$99.6685	$99.67	$99.65	$99.70
Purchase #5	$189.95	10.221%	$209.3648	$209.36	$209.35	$209.40
Purchase #6	$121.33	4.827%	$127.1866	$127.19	$127.20	$127.20
Purchase #7	$202.25	12.187%	$226.8982	$226.90	$226.90	$226.90
7 purchase totals =	$1,021.88		$1,105.1421	$1,105.14	$1,105.10	$1,105.20