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	$172.88	7.413%	$185.6956	$185.70	$185.70	$185.70
Purchase #2	$94.25	5.424%	$99.3621	$99.36	$99.35	$99.40
Purchase #3	$79.58	8.744%	$86.5385	$86.54	$86.55	$86.50
Purchase #4	$117.57	5.114%	$123.5825	$123.58	$123.60	$123.60
Purchase #5	$62.93	10.340%	$69.437	$69.44	$69.45	$69.40
Purchase #6	$201.85	4.482%	$210.8969	$210.90	$210.90	$210.90
Purchase #7	$32.49	10.527%	$35.9102	$35.91	$35.90	$35.90
7 purchase totals =	$761.55		$811.4228	$811.43	$811.45	$811.40