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	$83.67	10.869%	$92.7641	$92.76	$92.75	$92.80
Purchase #2	$217.63	7.737%	$234.468	$234.47	$234.45	$234.50
Purchase #3	$211.82	10.428%	$233.9086	$233.91	$233.90	$233.90
Purchase #4	$101.92	9.818%	$111.9265	$111.93	$111.95	$111.90
Purchase #5	$21.69	12.339%	$24.3663	$24.37	$24.35	$24.40
Purchase #6	$34.49	3.241%	$35.6078	$35.61	$35.60	$35.60
Purchase #7	$81.49	12.259%	$91.4799	$91.48	$91.50	$91.50
7 purchase totals =	$752.71		$824.5212	$824.53	$824.50	$824.60