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	$92.43	10.430%	$102.0704	$102.07	$102.05	$102.10
Purchase #2	$43.73	6.353%	$46.5082	$46.51	$46.50	$46.50
Purchase #3	$20.81	11.448%	$23.1923	$23.19	$23.20	$23.20
Purchase #4	$166.67	3.502%	$172.5068	$172.51	$172.50	$172.50
Purchase #5	$80.80	7.127%	$86.5586	$86.56	$86.55	$86.60
Purchase #6	$184.85	8.438%	$200.4476	$200.45	$200.45	$200.40
Purchase #7	$95.89	8.437%	$103.9802	$103.98	$104.00	$104.00
7 purchase totals =	$685.18		$735.2641	$735.27	$735.25	$735.30