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	$161.36	8.529%	$175.1224	$175.12	$175.10	$175.10
Purchase #2	$191.71	12.128%	$214.9606	$214.96	$214.95	$215.00
Purchase #3	$94.66	9.314%	$103.4766	$103.48	$103.50	$103.50
Purchase #4	$80.70	12.170%	$90.5212	$90.52	$90.50	$90.50
Purchase #5	$63.40	13.407%	$71.9	$71.90	$71.90	$71.90
Purchase #6	$97.75	11.852%	$109.3353	$109.34	$109.35	$109.30
Purchase #7	$150.33	3.583%	$155.7163	$155.72	$155.70	$155.70
7 purchase totals =	$839.91		$921.0324	$921.04	$921.00	$921.00