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	$120.41	9.237%	$131.5323	$131.53	$131.55	$131.50
Purchase #2	$213.95	6.210%	$227.2363	$227.24	$227.25	$227.20
Purchase #3	$213.60	6.496%	$227.4755	$227.48	$227.50	$227.50
Purchase #4	$79.83	12.508%	$89.8151	$89.82	$89.80	$89.80
Purchase #5	$59.97	7.319%	$64.3592	$64.36	$64.35	$64.40
Purchase #6	$13.57	6.471%	$14.4481	$14.45	$14.45	$14.40
Purchase #7	$245.50	13.447%	$278.5124	$278.51	$278.50	$278.50
7 purchase totals =	$946.83		$1,033.3789	$1,033.39	$1,033.40	$1,033.30