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	$187.97	13.246%	$212.8685	$212.87	$212.85	$212.90
Purchase #2	$75.96	5.362%	$80.033	$80.03	$80.05	$80.00
Purchase #3	$41.48	3.334%	$42.8629	$42.86	$42.85	$42.90
Purchase #4	$40.76	12.450%	$45.8346	$45.83	$45.85	$45.80
Purchase #5	$100.95	7.862%	$108.8867	$108.89	$108.90	$108.90
Purchase #6	$20.89	6.831%	$22.317	$22.32	$22.30	$22.30
Purchase #7	$91.87	3.814%	$95.3739	$95.37	$95.35	$95.40
7 purchase totals =	$559.88		$608.1766	$608.17	$608.15	$608.20