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	$167.85	11.712%	$187.5086	$187.51	$187.50	$187.50
Purchase #2	$203.66	6.525%	$216.9488	$216.95	$216.95	$216.90
Purchase #3	$81.63	6.695%	$87.0951	$87.10	$87.10	$87.10
Purchase #4	$52.73	7.285%	$56.5714	$56.57	$56.55	$56.60
Purchase #5	$41.39	10.609%	$45.7811	$45.78	$45.80	$45.80
Purchase #6	$148.87	10.371%	$164.3093	$164.31	$164.30	$164.30
Purchase #7	$182.76	9.781%	$200.6358	$200.64	$200.65	$200.60
7 purchase totals =	$878.89		$958.8501	$958.86	$958.85	$958.80