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	$43.75	10.779%	$48.4658	$48.47	$48.45	$48.50
Purchase #2	$193.56	7.168%	$207.4344	$207.43	$207.45	$207.40
Purchase #3	$51.82	4.700%	$54.2555	$54.26	$54.25	$54.30
Purchase #4	$168.86	5.182%	$177.6103	$177.61	$177.60	$177.60
Purchase #5	$221.33	6.417%	$235.5327	$235.53	$235.55	$235.50
Purchase #6	$139.91	3.112%	$144.264	$144.26	$144.25	$144.30
Purchase #7	$205.62	8.132%	$222.341	$222.34	$222.35	$222.30
7 purchase totals =	$1,024.85		$1,089.9037	$1,089.90	$1,089.90	$1,089.90