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	$9.58	9.380%	$10.4786	$10.48	$10.50	$10.50
Purchase #2	$8.55	4.364%	$8.9231	$8.92	$8.90	$8.90
Purchase #3	$127.94	13.802%	$145.5983	$145.60	$145.60	$145.60
Purchase #4	$71.37	9.315%	$78.0181	$78.02	$78.00	$78.00
Purchase #5	$168.58	9.799%	$185.0992	$185.10	$185.10	$185.10
Purchase #6	$38.50	9.744%	$42.2514	$42.25	$42.25	$42.30
Purchase #7	$214.39	11.753%	$239.5873	$239.59	$239.60	$239.60
7 purchase totals =	$638.91		$709.9560	$709.96	$709.95	$710.00