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	$158.57	12.422%	$178.2676	$178.27	$178.25	$178.30
Purchase #2	$92.29	10.283%	$101.7802	$101.78	$101.80	$101.80
Purchase #3	$193.83	10.165%	$213.5328	$213.53	$213.55	$213.50
Purchase #4	$157.93	3.833%	$163.9835	$163.98	$164.00	$164.00
Purchase #5	$165.50	5.460%	$174.5363	$174.54	$174.55	$174.50
Purchase #6	$163.27	12.839%	$184.2322	$184.23	$184.25	$184.20
Purchase #7	$78.52	6.393%	$83.5398	$83.54	$83.55	$83.50
7 purchase totals =	$1,009.91		$1,099.8724	$1,099.87	$1,099.95	$1,099.80