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	$117.90	8.499%	$127.9203	$127.92	$127.90	$127.90
Purchase #2	$170.95	9.849%	$187.7869	$187.79	$187.80	$187.80
Purchase #3	$140.95	4.472%	$147.2533	$147.25	$147.25	$147.30
Purchase #4	$247.55	3.273%	$255.6523	$255.65	$255.65	$255.70
Purchase #5	$92.48	11.246%	$102.8803	$102.88	$102.90	$102.90
Purchase #6	$146.97	6.531%	$156.5686	$156.57	$156.55	$156.60
Purchase #7	$183.55	9.237%	$200.5045	$200.50	$200.50	$200.50
7 purchase totals =	$1,100.35		$1,178.5662	$1,178.56	$1,178.55	$1,178.70