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	$148.79	10.404%	$164.2701	$164.27	$164.25	$164.30
Purchase #2	$162.60	10.594%	$179.8258	$179.83	$179.85	$179.80
Purchase #3	$210.71	8.423%	$228.4581	$228.46	$228.45	$228.50
Purchase #4	$186.65	13.146%	$211.187	$211.19	$211.20	$211.20
Purchase #5	$59.91	7.816%	$64.5926	$64.59	$64.60	$64.60
Purchase #6	$27.39	5.247%	$28.8272	$28.83	$28.85	$28.80
Purchase #7	$115.75	12.127%	$129.787	$129.79	$129.80	$129.80
7 purchase totals =	$911.80		$1,006.9478	$1,006.96	$1,007.00	$1,007.00