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	$30.81	9.112%	$33.6174	$33.62	$33.60	$33.60
Purchase #2	$194.64	6.150%	$206.6104	$206.61	$206.60	$206.60
Purchase #3	$86.85	3.377%	$89.7829	$89.78	$89.80	$89.80
Purchase #4	$77.92	6.601%	$83.0635	$83.06	$83.05	$83.10
Purchase #5	$148.47	12.845%	$167.541	$167.54	$167.55	$167.50
Purchase #6	$104.63	8.459%	$113.4807	$113.48	$113.50	$113.50
Purchase #7	$227.38	10.562%	$251.3959	$251.40	$251.40	$251.40
7 purchase totals =	$870.70		$945.4918	$945.49	$945.50	$945.50