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	$151.32	11.388%	$168.5523	$168.55	$168.55	$168.60
Purchase #2	$211.41	12.339%	$237.4959	$237.50	$237.50	$237.50
Purchase #3	$159.52	12.112%	$178.8411	$178.84	$178.85	$178.80
Purchase #4	$122.84	6.650%	$131.0089	$131.01	$131.00	$131.00
Purchase #5	$114.36	4.409%	$119.4021	$119.40	$119.40	$119.40
Purchase #6	$130.82	4.778%	$137.0706	$137.07	$137.05	$137.10
Purchase #7	$163.93	4.787%	$171.7773	$171.78	$171.80	$171.80
7 purchase totals =	$1,054.20		$1,144.1482	$1,144.15	$1,144.15	$1,144.20