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	$157.69	9.661%	$172.9244	$172.92	$172.90	$172.90
Purchase #2	$245.97	4.411%	$256.8197	$256.82	$256.80	$256.80
Purchase #3	$141.85	3.354%	$146.6076	$146.61	$146.60	$146.60
Purchase #4	$65.27	13.222%	$73.9	$73.90	$73.90	$73.90
Purchase #5	$156.83	9.172%	$171.2144	$171.21	$171.20	$171.20
Purchase #6	$207.98	9.467%	$227.6695	$227.67	$227.65	$227.70
Purchase #7	$234.85	4.139%	$244.5704	$244.57	$244.55	$244.60
7 purchase totals =	$1,210.44		$1,293.7060	$1,293.70	$1,293.60	$1,293.70