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	$58.96	8.198%	$63.7935	$63.79	$63.80	$63.80
Purchase #2	$99.59	13.823%	$113.3563	$113.36	$113.35	$113.40
Purchase #3	$105.35	13.468%	$119.5385	$119.54	$119.55	$119.50
Purchase #4	$132.83	4.127%	$138.3119	$138.31	$138.30	$138.30
Purchase #5	$69.38	13.679%	$78.8705	$78.87	$78.85	$78.90
Purchase #6	$64.44	12.604%	$72.562	$72.56	$72.55	$72.60
Purchase #7	$221.57	3.389%	$229.079	$229.08	$229.10	$229.10
7 purchase totals =	$752.12		$815.5117	$815.51	$815.50	$815.60