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	$192.51	7.189%	$206.3495	$206.35	$206.35	$206.30
Purchase #2	$153.86	9.175%	$167.9767	$167.98	$168.00	$168.00
Purchase #3	$125.73	3.413%	$130.0212	$130.02	$130.00	$130.00
Purchase #4	$38.88	4.507%	$40.6323	$40.63	$40.65	$40.60
Purchase #5	$80.72	10.776%	$89.4184	$89.42	$89.40	$89.40
Purchase #6	$83.42	8.610%	$90.6025	$90.60	$90.60	$90.60
Purchase #7	$184.55	3.117%	$190.3024	$190.30	$190.30	$190.30
7 purchase totals =	$859.67		$915.3030	$915.30	$915.30	$915.20