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	$180.30	8.459%	$195.5516	$195.55	$195.55	$195.60
Purchase #2	$104.69	12.691%	$117.9762	$117.98	$118.00	$118.00
Purchase #3	$119.59	3.110%	$123.3092	$123.31	$123.30	$123.30
Purchase #4	$127.76	13.749%	$145.3257	$145.33	$145.35	$145.30
Purchase #5	$123.40	9.405%	$135.0058	$135.01	$135.00	$135.00
Purchase #6	$84.60	10.590%	$93.5591	$93.56	$93.55	$93.60
Purchase #7	$81.80	10.129%	$90.0855	$90.09	$90.10	$90.10
7 purchase totals =	$822.14		$900.8131	$900.83	$900.85	$900.90