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	$179.62	9.360%	$196.4324	$196.43	$196.45	$196.40
Purchase #2	$160.70	4.572%	$168.0472	$168.05	$168.05	$168.00
Purchase #3	$156.52	4.152%	$163.0187	$163.02	$163.00	$163.00
Purchase #4	$41.36	3.749%	$42.9106	$42.91	$42.90	$42.90
Purchase #5	$131.84	11.203%	$146.61	$146.61	$146.60	$146.60
Purchase #6	$100.84	7.146%	$108.046	$108.05	$108.05	$108.00
Purchase #7	$69.37	4.368%	$72.4001	$72.40	$72.40	$72.40
7 purchase totals =	$840.25		$897.4650	$897.47	$897.45	$897.30