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	$157.81	5.735%	$166.8604	$166.86	$166.85	$166.90
Purchase #2	$163.36	5.550%	$172.4265	$172.43	$172.45	$172.40
Purchase #3	$209.77	12.524%	$236.0416	$236.04	$236.05	$236.00
Purchase #4	$174.97	13.359%	$198.3442	$198.34	$198.35	$198.30
Purchase #5	$78.25	11.211%	$87.0226	$87.02	$87.00	$87.00
Purchase #6	$141.90	11.543%	$158.2795	$158.28	$158.30	$158.30
Purchase #7	$83.75	7.659%	$90.1644	$90.16	$90.15	$90.20
7 purchase totals =	$1,009.81		$1,109.1392	$1,109.13	$1,109.15	$1,109.10