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	$85.85	12.869%	$96.898	$96.90	$96.90	$96.90
Purchase #2	$63.77	5.319%	$67.1619	$67.16	$67.15	$67.20
Purchase #3	$73.98	9.438%	$80.9622	$80.96	$80.95	$81.00
Purchase #4	$34.37	3.536%	$35.5853	$35.59	$35.60	$35.60
Purchase #5	$208.31	9.178%	$227.4287	$227.43	$227.45	$227.40
Purchase #6	$217.96	7.311%	$233.8951	$233.90	$233.90	$233.90
Purchase #7	$59.25	3.185%	$61.1371	$61.14	$61.15	$61.10
7 purchase totals =	$743.49		$803.0683	$803.08	$803.10	$803.10