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	$38.69	7.132%	$41.4494	$41.45	$41.45	$41.40
Purchase #2	$204.57	9.741%	$224.4972	$224.50	$224.50	$224.50
Purchase #3	$104.78	13.600%	$119.0301	$119.03	$119.05	$119.00
Purchase #4	$106.33	8.451%	$115.3159	$115.32	$115.30	$115.30
Purchase #5	$78.64	13.651%	$89.3751	$89.38	$89.40	$89.40
Purchase #6	$222.27	7.193%	$238.2579	$238.26	$238.25	$238.30
Purchase #7	$19.79	10.428%	$21.8537	$21.85	$21.85	$21.90
7 purchase totals =	$775.07		$849.7793	$849.79	$849.80	$849.80