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	$106.79	9.692%	$117.1401	$117.14	$117.15	$117.10
Purchase #2	$38.63	7.581%	$41.5585	$41.56	$41.55	$41.60
Purchase #3	$155.91	9.683%	$171.0068	$171.01	$171.00	$171.00
Purchase #4	$53.57	11.288%	$59.617	$59.62	$59.60	$59.60
Purchase #5	$228.62	8.452%	$247.943	$247.94	$247.95	$247.90
Purchase #6	$202.61	4.433%	$211.5917	$211.59	$211.60	$211.60
Purchase #7	$211.46	12.329%	$237.5309	$237.53	$237.55	$237.50
7 purchase totals =	$997.59		$1,086.3880	$1,086.39	$1,086.40	$1,086.30