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	$148.86	8.780%	$161.9299	$161.93	$161.95	$161.90
Purchase #2	$70.38	3.648%	$72.9475	$72.95	$72.95	$72.90
Purchase #3	$168.92	5.620%	$178.4133	$178.41	$178.40	$178.40
Purchase #4	$249.97	5.193%	$262.9509	$262.95	$262.95	$263.00
Purchase #5	$121.27	13.430%	$137.5566	$137.56	$137.55	$137.60
Purchase #6	$31.30	11.535%	$34.9105	$34.91	$34.90	$34.90
Purchase #7	$80.30	12.663%	$90.4684	$90.47	$90.45	$90.50
7 purchase totals =	$871.00		$939.1771	$939.18	$939.15	$939.20