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	$190.88	5.176%	$200.7599	$200.76	$200.75	$200.80
Purchase #2	$136.88	12.117%	$153.4657	$153.47	$153.45	$153.50
Purchase #3	$109.25	9.430%	$119.5523	$119.55	$119.55	$119.60
Purchase #4	$93.80	8.259%	$101.5469	$101.55	$101.55	$101.50
Purchase #5	$69.89	11.871%	$78.1866	$78.19	$78.20	$78.20
Purchase #6	$58.33	5.585%	$61.5877	$61.59	$61.60	$61.60
Purchase #7	$59.97	3.410%	$62.015	$62.02	$62.00	$62.00
7 purchase totals =	$719.00		$777.1141	$777.13	$777.10	$777.20