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	$119.48	5.712%	$126.3047	$126.30	$126.30	$126.30
Purchase #2	$215.57	11.861%	$241.1388	$241.14	$241.15	$241.10
Purchase #3	$183.98	13.297%	$208.4438	$208.44	$208.45	$208.40
Purchase #4	$90.89	5.765%	$96.1298	$96.13	$96.15	$96.10
Purchase #5	$228.50	13.214%	$258.694	$258.69	$258.70	$258.70
Purchase #6	$94.35	5.470%	$99.5109	$99.51	$99.50	$99.50
Purchase #7	$74.55	9.691%	$81.7746	$81.77	$81.75	$81.80
7 purchase totals =	$1,007.32		$1,111.9966	$1,111.98	$1,112.00	$1,111.90