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	$62.54	8.578%	$67.9047	$67.90	$67.90	$67.90
Purchase #2	$69.73	10.853%	$77.2978	$77.30	$77.30	$77.30
Purchase #3	$113.85	11.464%	$126.9018	$126.90	$126.90	$126.90
Purchase #4	$14.26	3.601%	$14.7735	$14.77	$14.75	$14.80
Purchase #5	$27.48	3.846%	$28.5369	$28.54	$28.55	$28.50
Purchase #6	$94.48	6.346%	$100.4757	$100.48	$100.50	$100.50
Purchase #7	$148.93	4.702%	$155.9327	$155.93	$155.95	$155.90
7 purchase totals =	$531.27		$571.8231	$571.82	$571.85	$571.80