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	$59.31	5.121%	$62.3473	$62.35	$62.35	$62.30
Purchase #2	$121.83	12.112%	$136.586	$136.59	$136.60	$136.60
Purchase #3	$242.67	9.588%	$265.9372	$265.94	$265.95	$265.90
Purchase #4	$200.83	10.233%	$221.3809	$221.38	$221.40	$221.40
Purchase #5	$180.95	4.717%	$189.4854	$189.49	$189.50	$189.50
Purchase #6	$128.38	8.337%	$139.083	$139.08	$139.10	$139.10
Purchase #7	$117.65	4.669%	$123.1431	$123.14	$123.15	$123.10
7 purchase totals =	$1,051.62		$1,137.9629	$1,137.97	$1,138.05	$1,137.90