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	$111.31	4.186%	$115.9694	$115.97	$115.95	$116.00
Purchase #2	$179.68	9.581%	$196.8951	$196.90	$196.90	$196.90
Purchase #3	$49.69	9.869%	$54.5939	$54.59	$54.60	$54.60
Purchase #4	$94.86	10.456%	$104.7786	$104.78	$104.80	$104.80
Purchase #5	$164.68	4.500%	$172.0906	$172.09	$172.10	$172.10
Purchase #6	$239.57	12.787%	$270.2038	$270.20	$270.20	$270.20
Purchase #7	$90.33	12.356%	$101.4912	$101.49	$101.50	$101.50
7 purchase totals =	$930.12		$1,016.0226	$1,016.02	$1,016.05	$1,016.10