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	$39.41	4.401%	$41.1444	$41.14	$41.15	$41.10
Purchase #2	$180.27	7.818%	$194.3635	$194.36	$194.35	$194.40
Purchase #3	$177.89	4.270%	$185.4859	$185.49	$185.50	$185.50
Purchase #4	$223.59	3.662%	$231.7779	$231.78	$231.80	$231.80
Purchase #5	$104.90	9.257%	$114.6106	$114.61	$114.60	$114.60
Purchase #6	$205.25	3.364%	$212.1546	$212.15	$212.15	$212.20
Purchase #7	$164.89	3.857%	$171.2498	$171.25	$171.25	$171.20
7 purchase totals =	$1,096.20		$1,150.7867	$1,150.78	$1,150.80	$1,150.80