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	$162.64	5.604%	$171.7543	$171.75	$171.75	$171.80
Purchase #2	$81.87	10.293%	$90.2969	$90.30	$90.30	$90.30
Purchase #3	$61.91	7.864%	$66.7786	$66.78	$66.80	$66.80
Purchase #4	$6.54	13.291%	$7.4092	$7.41	$7.40	$7.40
Purchase #5	$182.64	9.271%	$199.5726	$199.57	$199.55	$199.60
Purchase #6	$37.73	10.192%	$41.5754	$41.58	$41.60	$41.60
Purchase #7	$94.49	4.703%	$98.9339	$98.93	$98.95	$98.90
7 purchase totals =	$627.82		$676.3209	$676.32	$676.35	$676.40