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	$187.61	13.461%	$212.8642	$212.86	$212.85	$212.90
Purchase #2	$188.71	13.654%	$214.4765	$214.48	$214.50	$214.50
Purchase #3	$15.93	7.850%	$17.1805	$17.18	$17.20	$17.20
Purchase #4	$208.89	10.630%	$231.095	$231.10	$231.10	$231.10
Purchase #5	$152.42	8.790%	$165.8177	$165.82	$165.80	$165.80
Purchase #6	$103.89	9.616%	$113.8801	$113.88	$113.90	$113.90
Purchase #7	$146.93	11.826%	$164.3059	$164.31	$164.30	$164.30
7 purchase totals =	$1,004.38		$1,119.6199	$1,119.63	$1,119.65	$1,119.70