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	$165.92	7.639%	$178.5946	$178.59	$178.60	$178.60
Purchase #2	$219.99	13.542%	$249.781	$249.78	$249.80	$249.80
Purchase #3	$231.35	7.657%	$249.0645	$249.06	$249.05	$249.10
Purchase #4	$59.39	4.490%	$62.0566	$62.06	$62.05	$62.10
Purchase #5	$156.34	5.372%	$164.7386	$164.74	$164.75	$164.70
Purchase #6	$78.47	3.185%	$80.9693	$80.97	$80.95	$81.00
Purchase #7	$72.37	13.645%	$82.2449	$82.24	$82.25	$82.20
7 purchase totals =	$983.83		$1,067.4495	$1,067.44	$1,067.45	$1,067.50