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	$169.60	4.635%	$177.461	$177.46	$177.45	$177.50
Purchase #2	$192.81	9.638%	$211.393	$211.39	$211.40	$211.40
Purchase #3	$60.55	11.602%	$67.575	$67.58	$67.60	$67.60
Purchase #4	$87.32	5.619%	$92.2265	$92.23	$92.25	$92.20
Purchase #5	$51.74	5.591%	$54.6328	$54.63	$54.65	$54.60
Purchase #6	$54.84	12.842%	$61.8826	$61.88	$61.90	$61.90
Purchase #7	$151.44	3.630%	$156.9373	$156.94	$156.95	$156.90
7 purchase totals =	$768.30		$822.1082	$822.11	$822.20	$822.10