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	$106.45	7.780%	$114.7318	$114.73	$114.75	$114.70
Purchase #2	$166.77	7.553%	$179.3661	$179.37	$179.35	$179.40
Purchase #3	$221.79	3.282%	$229.0691	$229.07	$229.05	$229.10
Purchase #4	$116.48	13.225%	$131.8845	$131.88	$131.90	$131.90
Purchase #5	$121.33	13.578%	$137.8042	$137.80	$137.80	$137.80
Purchase #6	$45.25	10.328%	$49.9234	$49.92	$49.90	$49.90
Purchase #7	$159.47	5.526%	$168.2823	$168.28	$168.30	$168.30
7 purchase totals =	$937.54		$1,011.0614	$1,011.05	$1,011.05	$1,011.10