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	$153.97	8.447%	$166.9758	$166.98	$167.00	$167.00
Purchase #2	$30.31	10.465%	$33.4819	$33.48	$33.50	$33.50
Purchase #3	$119.43	12.630%	$134.514	$134.51	$134.50	$134.50
Purchase #4	$187.72	6.578%	$200.0682	$200.07	$200.05	$200.10
Purchase #5	$237.75	11.174%	$264.3162	$264.32	$264.30	$264.30
Purchase #6	$63.37	6.723%	$67.6304	$67.63	$67.65	$67.60
Purchase #7	$77.40	3.468%	$80.0842	$80.08	$80.10	$80.10
7 purchase totals =	$869.95		$947.0707	$947.07	$947.10	$947.10