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	$126.44	3.802%	$131.2472	$131.25	$131.25	$131.20
Purchase #2	$187.47	3.737%	$194.4758	$194.48	$194.50	$194.50
Purchase #3	$134.45	10.532%	$148.6103	$148.61	$148.60	$148.60
Purchase #4	$112.73	6.322%	$119.8568	$119.86	$119.85	$119.90
Purchase #5	$164.48	4.212%	$171.4079	$171.41	$171.40	$171.40
Purchase #6	$219.31	12.242%	$246.1579	$246.16	$246.15	$246.20
Purchase #7	$102.87	6.358%	$109.4105	$109.41	$109.40	$109.40
7 purchase totals =	$1,047.75		$1,121.1664	$1,121.18	$1,121.15	$1,121.20