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	$162.59	10.559%	$179.7579	$179.76	$179.75	$179.80
Purchase #2	$174.77	5.738%	$184.7983	$184.80	$184.80	$184.80
Purchase #3	$83.85	7.610%	$90.231	$90.23	$90.25	$90.20
Purchase #4	$201.87	12.860%	$227.8305	$227.83	$227.85	$227.80
Purchase #5	$61.49	6.577%	$65.5342	$65.53	$65.55	$65.50
Purchase #6	$152.71	5.203%	$160.6555	$160.66	$160.65	$160.70
Purchase #7	$43.94	3.252%	$45.3689	$45.37	$45.35	$45.40
7 purchase totals =	$881.22		$954.1763	$954.18	$954.20	$954.20