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	$84.68	6.134%	$89.8743	$89.87	$89.85	$89.90
Purchase #2	$168.60	5.534%	$177.9303	$177.93	$177.95	$177.90
Purchase #3	$86.94	6.427%	$92.5276	$92.53	$92.55	$92.50
Purchase #4	$209.85	13.171%	$237.4893	$237.49	$237.50	$237.50
Purchase #5	$246.43	3.770%	$255.7204	$255.72	$255.70	$255.70
Purchase #6	$7.65	3.276%	$7.9006	$7.90	$7.90	$7.90
Purchase #7	$169.58	7.679%	$182.602	$182.60	$182.60	$182.60
7 purchase totals =	$973.73		$1,044.0445	$1,044.04	$1,044.05	$1,044.00