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	$167.54	12.368%	$188.2613	$188.26	$188.25	$188.30
Purchase #2	$36.50	11.194%	$40.5858	$40.59	$40.60	$40.60
Purchase #3	$66.79	10.360%	$73.7094	$73.71	$73.70	$73.70
Purchase #4	$242.86	8.845%	$264.341	$264.34	$264.35	$264.30
Purchase #5	$190.34	9.867%	$209.1208	$209.12	$209.10	$209.10
Purchase #6	$106.35	5.294%	$111.9802	$111.98	$112.00	$112.00
Purchase #7	$151.69	10.535%	$167.6705	$167.67	$167.65	$167.70
7 purchase totals =	$962.07		$1,055.6690	$1,055.67	$1,055.65	$1,055.70