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	$219.47	8.563%	$238.2632	$238.26	$238.25	$238.30
Purchase #2	$183.79	10.227%	$202.5862	$202.59	$202.60	$202.60
Purchase #3	$141.25	5.156%	$148.5329	$148.53	$148.55	$148.50
Purchase #4	$94.25	9.829%	$103.5138	$103.51	$103.50	$103.50
Purchase #5	$221.92	8.176%	$240.0642	$240.06	$240.05	$240.10
Purchase #6	$80.57	11.570%	$89.8919	$89.89	$89.90	$89.90
Purchase #7	$171.54	5.573%	$181.0999	$181.10	$181.10	$181.10
7 purchase totals =	$1,112.79		$1,203.9521	$1,203.94	$1,203.95	$1,204.00