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	$152.71	9.336%	$166.967	$166.97	$166.95	$167.00
Purchase #2	$117.33	7.673%	$126.3327	$126.33	$126.35	$126.30
Purchase #3	$127.39	8.778%	$138.5723	$138.57	$138.55	$138.60
Purchase #4	$142.56	5.233%	$150.0202	$150.02	$150.00	$150.00
Purchase #5	$53.87	9.860%	$59.1816	$59.18	$59.20	$59.20
Purchase #6	$98.41	9.660%	$107.9164	$107.92	$107.90	$107.90
Purchase #7	$36.28	3.137%	$37.4181	$37.42	$37.40	$37.40
7 purchase totals =	$728.55		$786.4083	$786.41	$786.35	$786.40