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	$202.52	12.289%	$227.4077	$227.41	$227.40	$227.40
Purchase #2	$179.73	3.274%	$185.6144	$185.61	$185.60	$185.60
Purchase #3	$92.37	13.265%	$104.6229	$104.62	$104.60	$104.60
Purchase #4	$111.94	10.645%	$123.856	$123.86	$123.85	$123.90
Purchase #5	$153.25	5.143%	$161.1316	$161.13	$161.15	$161.10
Purchase #6	$213.45	5.570%	$225.3392	$225.34	$225.35	$225.30
Purchase #7	$33.79	3.470%	$34.9625	$34.96	$34.95	$35.00
7 purchase totals =	$987.05		$1,062.9343	$1,062.93	$1,062.90	$1,062.90