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	$148.31	10.638%	$164.0872	$164.09	$164.10	$164.10
Purchase #2	$128.65	5.734%	$136.0268	$136.03	$136.05	$136.00
Purchase #3	$195.66	5.135%	$205.7071	$205.71	$205.70	$205.70
Purchase #4	$125.42	11.527%	$139.8772	$139.88	$139.90	$139.90
Purchase #5	$181.51	10.663%	$200.8644	$200.86	$200.85	$200.90
Purchase #6	$42.65	9.148%	$46.5516	$46.55	$46.55	$46.60
Purchase #7	$31.31	4.430%	$32.697	$32.70	$32.70	$32.70
7 purchase totals =	$853.51		$925.8113	$925.82	$925.85	$925.90