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	$41.89	4.262%	$43.6754	$43.68	$43.70	$43.70
Purchase #2	$144.94	13.813%	$164.9606	$164.96	$164.95	$165.00
Purchase #3	$112.98	5.664%	$119.3792	$119.38	$119.40	$119.40
Purchase #4	$231.42	4.413%	$241.6326	$241.63	$241.65	$241.60
Purchase #5	$142.37	4.187%	$148.331	$148.33	$148.35	$148.30
Purchase #6	$129.78	4.817%	$136.0315	$136.03	$136.05	$136.00
Purchase #7	$112.95	9.435%	$123.6068	$123.61	$123.60	$123.60
7 purchase totals =	$916.33		$977.6171	$977.62	$977.70	$977.60