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	$81.65	4.373%	$85.2206	$85.22	$85.20	$85.20
Purchase #2	$41.31	6.510%	$43.9993	$44.00	$44.00	$44.00
Purchase #3	$101.92	9.135%	$111.2304	$111.23	$111.25	$111.20
Purchase #4	$75.86	7.307%	$81.4031	$81.40	$81.40	$81.40
Purchase #5	$85.71	4.805%	$89.8284	$89.83	$89.85	$89.80
Purchase #6	$208.38	11.193%	$231.704	$231.70	$231.70	$231.70
Purchase #7	$20.54	7.190%	$22.0168	$22.02	$22.00	$22.00
7 purchase totals =	$615.37		$665.4026	$665.40	$665.40	$665.30