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	$168.50	11.309%	$187.5557	$187.56	$187.55	$187.60
Purchase #2	$152.61	8.509%	$165.5956	$165.60	$165.60	$165.60
Purchase #3	$150.31	11.502%	$167.5987	$167.60	$167.60	$167.60
Purchase #4	$29.51	8.209%	$31.9325	$31.93	$31.95	$31.90
Purchase #5	$93.70	4.695%	$98.0992	$98.10	$98.10	$98.10
Purchase #6	$132.29	5.614%	$139.7168	$139.72	$139.70	$139.70
Purchase #7	$182.79	11.586%	$203.968	$203.97	$203.95	$204.00
7 purchase totals =	$909.71		$994.4665	$994.48	$994.45	$994.50