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	$159.94	4.577%	$167.2605	$167.26	$167.25	$167.30
Purchase #2	$78.34	9.687%	$85.9288	$85.93	$85.95	$85.90
Purchase #3	$82.61	9.520%	$90.4745	$90.47	$90.45	$90.50
Purchase #4	$143.41	5.865%	$151.821	$151.82	$151.80	$151.80
Purchase #5	$213.36	13.509%	$242.1828	$242.18	$242.20	$242.20
Purchase #6	$31.25	4.825%	$32.7578	$32.76	$32.75	$32.80
Purchase #7	$15.78	7.867%	$17.0214	$17.02	$17.00	$17.00
7 purchase totals =	$724.69		$787.4468	$787.44	$787.40	$787.50