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	$86.83	7.544%	$93.3805	$93.38	$93.40	$93.40
Purchase #2	$37.59	13.648%	$42.7203	$42.72	$42.70	$42.70
Purchase #3	$16.81	9.384%	$18.3875	$18.39	$18.40	$18.40
Purchase #4	$44.60	8.248%	$48.2786	$48.28	$48.30	$48.30
Purchase #5	$101.55	3.767%	$105.3754	$105.38	$105.40	$105.40
Purchase #6	$78.78	7.102%	$84.375	$84.38	$84.40	$84.40
Purchase #7	$67.67	8.753%	$73.5932	$73.59	$73.60	$73.60
7 purchase totals =	$433.83		$466.1105	$466.12	$466.20	$466.20