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	$44.81	8.425%	$48.5852	$48.59	$48.60	$48.60
Purchase #2	$141.86	11.386%	$158.0122	$158.01	$158.00	$158.00
Purchase #3	$92.45	5.729%	$97.7465	$97.75	$97.75	$97.70
Purchase #4	$98.73	11.330%	$109.9161	$109.92	$109.90	$109.90
Purchase #5	$137.45	3.622%	$142.4284	$142.43	$142.45	$142.40
Purchase #6	$238.35	9.312%	$260.5452	$260.55	$260.55	$260.50
Purchase #7	$221.27	3.499%	$229.0122	$229.01	$229.00	$229.00
7 purchase totals =	$974.92		$1,046.2458	$1,046.26	$1,046.25	$1,046.10