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	$36.32	4.758%	$38.0481	$38.05	$38.05	$38.00
Purchase #2	$5.75	13.786%	$6.5427	$6.54	$6.55	$6.50
Purchase #3	$188.76	6.365%	$200.7746	$200.77	$200.75	$200.80
Purchase #4	$99.42	5.762%	$105.1486	$105.15	$105.15	$105.10
Purchase #5	$124.74	7.772%	$134.4348	$134.43	$134.45	$134.40
Purchase #6	$180.55	12.332%	$202.8154	$202.82	$202.80	$202.80
Purchase #7	$75.53	3.791%	$78.3933	$78.39	$78.40	$78.40
7 purchase totals =	$711.07		$766.1575	$766.15	$766.15	$766.00