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	$32.83	11.416%	$36.5779	$36.58	$36.60	$36.60
Purchase #2	$178.70	9.537%	$195.7426	$195.74	$195.75	$195.70
Purchase #3	$81.95	11.722%	$91.5562	$91.56	$91.55	$91.60
Purchase #4	$105.53	4.710%	$110.5005	$110.50	$110.50	$110.50
Purchase #5	$76.59	11.610%	$85.4821	$85.48	$85.50	$85.50
Purchase #6	$158.30	6.314%	$168.2951	$168.30	$168.30	$168.30
Purchase #7	$173.32	8.242%	$187.605	$187.61	$187.60	$187.60
7 purchase totals =	$807.22		$875.7594	$875.77	$875.80	$875.80