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	$163.78	13.460%	$185.8248	$185.82	$185.80	$185.80
Purchase #2	$75.38	8.366%	$81.6863	$81.69	$81.70	$81.70
Purchase #3	$93.60	4.806%	$98.0984	$98.10	$98.10	$98.10
Purchase #4	$154.90	6.194%	$164.4945	$164.49	$164.50	$164.50
Purchase #5	$91.51	9.143%	$99.8768	$99.88	$99.90	$99.90
Purchase #6	$136.54	13.522%	$155.0029	$155.00	$155.00	$155.00
Purchase #7	$93.59	9.516%	$102.496	$102.50	$102.50	$102.50
7 purchase totals =	$809.30		$887.4797	$887.48	$887.50	$887.50