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	$33.96	11.387%	$37.827	$37.83	$37.85	$37.80
Purchase #2	$186.92	10.165%	$205.9204	$205.92	$205.90	$205.90
Purchase #3	$56.92	13.476%	$64.5905	$64.59	$64.60	$64.60
Purchase #4	$195.41	10.196%	$215.334	$215.33	$215.35	$215.30
Purchase #5	$167.33	11.710%	$186.9243	$186.92	$186.90	$186.90
Purchase #6	$127.44	5.674%	$134.6709	$134.67	$134.65	$134.70
Purchase #7	$188.76	11.126%	$209.7614	$209.76	$209.75	$209.80
7 purchase totals =	$956.74		$1,055.0285	$1,055.02	$1,055.00	$1,055.00