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	$86.96	3.352%	$89.8749	$89.87	$89.85	$89.90
Purchase #2	$86.95	3.709%	$90.175	$90.18	$90.20	$90.20
Purchase #3	$228.85	8.493%	$248.2862	$248.29	$248.30	$248.30
Purchase #4	$151.83	10.834%	$168.2793	$168.28	$168.30	$168.30
Purchase #5	$87.92	11.733%	$98.2357	$98.24	$98.25	$98.20
Purchase #6	$198.72	6.415%	$211.4679	$211.47	$211.45	$211.50
Purchase #7	$82.50	4.379%	$86.1127	$86.11	$86.10	$86.10
7 purchase totals =	$923.73		$992.4317	$992.44	$992.45	$992.50