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	$119.58	9.862%	$131.373	$131.37	$131.35	$131.40
Purchase #2	$35.25	12.370%	$39.6104	$39.61	$39.60	$39.60
Purchase #3	$92.56	3.282%	$95.5978	$95.60	$95.60	$95.60
Purchase #4	$240.48	7.558%	$258.6555	$258.66	$258.65	$258.70
Purchase #5	$168.95	4.333%	$176.2706	$176.27	$176.25	$176.30
Purchase #6	$139.67	8.483%	$151.5182	$151.52	$151.50	$151.50
Purchase #7	$96.29	3.701%	$99.8537	$99.85	$99.85	$99.90
7 purchase totals =	$892.78		$952.8792	$952.88	$952.80	$953.00