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	$185.92	10.667%	$205.7521	$205.75	$205.75	$205.80
Purchase #2	$85.73	11.339%	$95.4509	$95.45	$95.45	$95.50
Purchase #3	$96.99	5.662%	$102.4816	$102.48	$102.50	$102.50
Purchase #4	$32.82	8.125%	$35.4866	$35.49	$35.50	$35.50
Purchase #5	$177.75	4.561%	$185.8572	$185.86	$185.85	$185.90
Purchase #6	$205.74	6.530%	$219.1748	$219.17	$219.15	$219.20
Purchase #7	$155.98	6.471%	$166.0735	$166.07	$166.05	$166.10
7 purchase totals =	$940.93		$1,010.2767	$1,010.27	$1,010.25	$1,010.50