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	$164.36	10.432%	$181.506	$181.51	$181.50	$181.50
Purchase #2	$245.47	5.656%	$259.3538	$259.35	$259.35	$259.40
Purchase #3	$130.67	5.690%	$138.1051	$138.11	$138.10	$138.10
Purchase #4	$141.71	7.874%	$152.8682	$152.87	$152.85	$152.90
Purchase #5	$38.77	11.157%	$43.0956	$43.10	$43.10	$43.10
Purchase #6	$96.80	13.214%	$109.5912	$109.59	$109.60	$109.60
Purchase #7	$198.55	12.242%	$222.8565	$222.86	$222.85	$222.90
7 purchase totals =	$1,016.33		$1,107.3764	$1,107.39	$1,107.35	$1,107.50