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	$168.66	13.658%	$191.6956	$191.70	$191.70	$191.70
Purchase #2	$136.93	5.172%	$144.012	$144.01	$144.00	$144.00
Purchase #3	$52.53	11.179%	$58.4023	$58.40	$58.40	$58.40
Purchase #4	$90.83	4.699%	$95.0981	$95.10	$95.10	$95.10
Purchase #5	$85.98	7.238%	$92.2032	$92.20	$92.20	$92.20
Purchase #6	$34.52	10.855%	$38.2671	$38.27	$38.25	$38.30
Purchase #7	$226.44	7.687%	$243.8464	$243.85	$243.85	$243.80
7 purchase totals =	$795.89		$863.5247	$863.53	$863.50	$863.50