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	$144.91	9.352%	$158.462	$158.46	$158.45	$158.50
Purchase #2	$235.41	5.645%	$248.6989	$248.70	$248.70	$248.70
Purchase #3	$96.35	6.337%	$102.4557	$102.46	$102.45	$102.50
Purchase #4	$116.98	5.570%	$123.4958	$123.50	$123.50	$123.50
Purchase #5	$141.53	10.803%	$156.8195	$156.82	$156.80	$156.80
Purchase #6	$101.60	11.533%	$113.3175	$113.32	$113.30	$113.30
Purchase #7	$195.80	3.332%	$202.3241	$202.32	$202.30	$202.30
7 purchase totals =	$1,032.58		$1,105.5735	$1,105.58	$1,105.50	$1,105.60