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	$228.30	7.764%	$246.0252	$246.03	$246.05	$246.00
Purchase #2	$26.48	6.803%	$28.2814	$28.28	$28.30	$28.30
Purchase #3	$62.59	5.320%	$65.9198	$65.92	$65.90	$65.90
Purchase #4	$85.86	5.552%	$90.6269	$90.63	$90.65	$90.60
Purchase #5	$166.85	3.455%	$172.6147	$172.61	$172.60	$172.60
Purchase #6	$50.72	11.297%	$56.4498	$56.45	$56.45	$56.40
Purchase #7	$203.52	7.419%	$218.6191	$218.62	$218.60	$218.60
7 purchase totals =	$824.32		$878.5369	$878.54	$878.55	$878.40