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	$111.39	3.804%	$115.6273	$115.63	$115.65	$115.60
Purchase #2	$24.55	13.279%	$27.81	$27.81	$27.80	$27.80
Purchase #3	$109.64	8.207%	$118.6382	$118.64	$118.65	$118.60
Purchase #4	$58.82	13.443%	$66.7272	$66.73	$66.75	$66.70
Purchase #5	$73.25	9.800%	$80.4285	$80.43	$80.45	$80.40
Purchase #6	$179.39	11.571%	$200.1472	$200.15	$200.15	$200.10
Purchase #7	$59.85	3.404%	$61.8873	$61.89	$61.90	$61.90
7 purchase totals =	$616.89		$671.2657	$671.28	$671.35	$671.10