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	$195.62	10.331%	$215.8295	$215.83	$215.85	$215.80
Purchase #2	$214.97	10.729%	$238.0341	$238.03	$238.05	$238.00
Purchase #3	$182.80	7.228%	$196.0128	$196.01	$196.00	$196.00
Purchase #4	$5.53	12.774%	$6.2364	$6.24	$6.25	$6.20
Purchase #5	$19.65	4.191%	$20.4735	$20.47	$20.45	$20.50
Purchase #6	$54.55	9.578%	$59.7748	$59.77	$59.75	$59.80
Purchase #7	$93.86	7.173%	$100.5926	$100.59	$100.60	$100.60
7 purchase totals =	$766.98		$836.9537	$836.94	$836.95	$836.90