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	$80.45	7.179%	$86.2255	$86.23	$86.25	$86.20
Purchase #2	$47.76	9.642%	$52.365	$52.37	$52.35	$52.40
Purchase #3	$80.27	13.709%	$91.2742	$91.27	$91.25	$91.30
Purchase #4	$250.62	4.605%	$262.1611	$262.16	$262.15	$262.20
Purchase #5	$122.61	4.240%	$127.8087	$127.81	$127.80	$127.80
Purchase #6	$204.51	4.279%	$213.261	$213.26	$213.25	$213.30
Purchase #7	$29.60	7.856%	$31.9254	$31.93	$31.95	$31.90
7 purchase totals =	$815.82		$865.0209	$865.03	$865.00	$865.10