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	$168.61	4.440%	$176.0963	$176.10	$176.10	$176.10
Purchase #2	$134.57	6.487%	$143.2996	$143.30	$143.30	$143.30
Purchase #3	$206.80	8.760%	$224.9157	$224.92	$224.90	$224.90
Purchase #4	$56.53	9.258%	$61.7635	$61.76	$61.75	$61.80
Purchase #5	$188.94	13.349%	$214.1616	$214.16	$214.15	$214.20
Purchase #6	$69.33	13.380%	$78.6064	$78.61	$78.60	$78.60
Purchase #7	$172.58	8.700%	$187.5945	$187.59	$187.60	$187.60
7 purchase totals =	$997.36		$1,086.4376	$1,086.44	$1,086.40	$1,086.50