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	$218.35	12.591%	$245.8424	$245.84	$245.85	$245.80
Purchase #2	$34.52	11.662%	$38.5457	$38.55	$38.55	$38.50
Purchase #3	$30.42	4.725%	$31.8573	$31.86	$31.85	$31.90
Purchase #4	$86.39	4.786%	$90.5246	$90.52	$90.50	$90.50
Purchase #5	$152.60	7.855%	$164.5867	$164.59	$164.60	$164.60
Purchase #6	$53.78	11.608%	$60.0228	$60.02	$60.00	$60.00
Purchase #7	$228.90	4.529%	$239.2669	$239.27	$239.25	$239.30
7 purchase totals =	$804.96		$870.6464	$870.65	$870.60	$870.60