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	$150.94	4.322%	$157.4636	$157.46	$157.45	$157.50
Purchase #2	$28.62	12.679%	$32.2487	$32.25	$32.25	$32.20
Purchase #3	$167.49	13.160%	$189.5317	$189.53	$189.55	$189.50
Purchase #4	$63.59	13.615%	$72.2478	$72.25	$72.25	$72.20
Purchase #5	$131.66	10.672%	$145.7108	$145.71	$145.70	$145.70
Purchase #6	$156.89	3.368%	$162.1741	$162.17	$162.15	$162.20
Purchase #7	$169.66	7.611%	$182.5728	$182.57	$182.55	$182.60
7 purchase totals =	$868.85		$941.9495	$941.94	$941.90	$941.90