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	$87.93	9.813%	$96.5586	$96.56	$96.55	$96.60
Purchase #2	$241.91	9.209%	$264.1875	$264.19	$264.20	$264.20
Purchase #3	$25.70	10.620%	$28.4293	$28.43	$28.45	$28.40
Purchase #4	$82.85	9.458%	$90.686	$90.69	$90.70	$90.70
Purchase #5	$239.29	7.768%	$257.878	$257.88	$257.90	$257.90
Purchase #6	$135.60	11.232%	$150.8306	$150.83	$150.85	$150.80
Purchase #7	$144.82	13.413%	$164.2447	$164.24	$164.25	$164.20
7 purchase totals =	$958.10		$1,052.8147	$1,052.82	$1,052.90	$1,052.80