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	$213.81	6.346%	$227.3784	$227.38	$227.40	$227.40
Purchase #2	$78.36	5.107%	$82.3618	$82.36	$82.35	$82.40
Purchase #3	$96.76	7.487%	$104.0044	$104.00	$104.00	$104.00
Purchase #4	$55.32	13.621%	$62.8551	$62.86	$62.85	$62.90
Purchase #5	$177.96	5.232%	$187.2709	$187.27	$187.25	$187.30
Purchase #6	$177.60	11.853%	$198.6509	$198.65	$198.65	$198.70
Purchase #7	$127.25	9.802%	$139.723	$139.72	$139.70	$139.70
7 purchase totals =	$927.06		$1,002.2445	$1,002.24	$1,002.20	$1,002.40