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	$239.96	10.154%	$264.3255	$264.33	$264.35	$264.30
Purchase #2	$52.44	12.796%	$59.1502	$59.15	$59.15	$59.20
Purchase #3	$37.57	12.128%	$42.1265	$42.13	$42.15	$42.10
Purchase #4	$237.46	10.608%	$262.6498	$262.65	$262.65	$262.60
Purchase #5	$246.49	11.466%	$274.7525	$274.75	$274.75	$274.80
Purchase #6	$85.55	11.627%	$95.4969	$95.50	$95.50	$95.50
Purchase #7	$113.59	5.269%	$119.5751	$119.58	$119.60	$119.60
7 purchase totals =	$1,013.06		$1,118.0765	$1,118.09	$1,118.15	$1,118.10