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	$166.32	7.105%	$178.137	$178.14	$178.15	$178.10
Purchase #2	$20.86	6.292%	$22.1725	$22.17	$22.15	$22.20
Purchase #3	$164.55	4.475%	$171.9136	$171.91	$171.90	$171.90
Purchase #4	$106.84	4.523%	$111.6724	$111.67	$111.65	$111.70
Purchase #5	$135.88	5.320%	$143.1088	$143.11	$143.10	$143.10
Purchase #6	$224.53	3.873%	$233.226	$233.23	$233.25	$233.20
Purchase #7	$139.88	3.190%	$144.3422	$144.34	$144.35	$144.30
7 purchase totals =	$958.86		$1,004.5725	$1,004.57	$1,004.55	$1,004.50