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	$103.46	8.812%	$112.5769	$112.58	$112.60	$112.60
Purchase #2	$204.80	8.683%	$222.5828	$222.58	$222.60	$222.60
Purchase #3	$76.40	7.644%	$82.24	$82.24	$82.25	$82.20
Purchase #4	$166.73	11.830%	$186.4542	$186.45	$186.45	$186.50
Purchase #5	$148.95	10.546%	$164.6583	$164.66	$164.65	$164.70
Purchase #6	$32.30	3.554%	$33.4479	$33.45	$33.45	$33.40
Purchase #7	$91.47	13.791%	$104.0846	$104.08	$104.10	$104.10
7 purchase totals =	$824.11		$906.0447	$906.04	$906.10	$906.10