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	$154.56	7.700%	$166.4611	$166.46	$166.45	$166.50
Purchase #2	$104.67	8.767%	$113.8464	$113.85	$113.85	$113.80
Purchase #3	$135.45	4.229%	$141.1782	$141.18	$141.20	$141.20
Purchase #4	$71.50	4.697%	$74.8584	$74.86	$74.85	$74.90
Purchase #5	$214.93	6.245%	$228.3524	$228.35	$228.35	$228.40
Purchase #6	$27.51	4.873%	$28.8506	$28.85	$28.85	$28.90
Purchase #7	$158.59	8.168%	$171.5436	$171.54	$171.55	$171.50
7 purchase totals =	$867.21		$925.0907	$925.09	$925.10	$925.20