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	$49.81	11.525%	$55.5506	$55.55	$55.55	$55.60
Purchase #2	$90.89	8.482%	$98.5993	$98.60	$98.60	$98.60
Purchase #3	$194.83	3.757%	$202.1498	$202.15	$202.15	$202.10
Purchase #4	$236.72	8.369%	$256.5311	$256.53	$256.55	$256.50
Purchase #5	$123.47	12.125%	$138.4407	$138.44	$138.45	$138.40
Purchase #6	$153.83	8.314%	$166.6194	$166.62	$166.60	$166.60
Purchase #7	$162.73	6.269%	$172.9315	$172.93	$172.95	$172.90
7 purchase totals =	$1,012.28		$1,090.8224	$1,090.82	$1,090.85	$1,090.70