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	$76.56	10.145%	$84.327	$84.33	$84.35	$84.30
Purchase #2	$213.91	3.267%	$220.8984	$220.90	$220.90	$220.90
Purchase #3	$24.75	4.759%	$25.9279	$25.93	$25.95	$25.90
Purchase #4	$199.53	11.493%	$222.462	$222.46	$222.45	$222.50
Purchase #5	$112.50	9.871%	$123.6049	$123.60	$123.60	$123.60
Purchase #6	$184.61	5.801%	$195.3192	$195.32	$195.30	$195.30
Purchase #7	$56.27	9.324%	$61.5166	$61.52	$61.50	$61.50
7 purchase totals =	$868.13		$934.0560	$934.06	$934.05	$934.00