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	$179.98	11.635%	$200.9207	$200.92	$200.90	$200.90
Purchase #2	$213.39	5.260%	$224.6143	$224.61	$224.60	$224.60
Purchase #3	$185.90	10.774%	$205.9289	$205.93	$205.95	$205.90
Purchase #4	$148.26	12.394%	$166.6353	$166.64	$166.65	$166.60
Purchase #5	$91.40	11.277%	$101.7072	$101.71	$101.70	$101.70
Purchase #6	$78.31	3.755%	$81.2505	$81.25	$81.25	$81.30
Purchase #7	$54.42	9.726%	$59.7129	$59.71	$59.70	$59.70
7 purchase totals =	$951.66		$1,040.7698	$1,040.77	$1,040.75	$1,040.70