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	$115.35	3.557%	$119.453	$119.45	$119.45	$119.50
Purchase #2	$19.46	5.568%	$20.5435	$20.54	$20.55	$20.50
Purchase #3	$38.56	5.395%	$40.6403	$40.64	$40.65	$40.60
Purchase #4	$22.59	8.176%	$24.437	$24.44	$24.45	$24.40
Purchase #5	$125.54	13.553%	$142.5544	$142.55	$142.55	$142.60
Purchase #6	$220.67	13.489%	$250.4362	$250.44	$250.45	$250.40
Purchase #7	$154.33	5.281%	$162.4802	$162.48	$162.50	$162.50
7 purchase totals =	$696.50		$760.5446	$760.54	$760.60	$760.50