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	$229.85	8.684%	$249.8102	$249.81	$249.80	$249.80
Purchase #2	$156.85	11.547%	$174.9615	$174.96	$174.95	$175.00
Purchase #3	$71.93	7.254%	$77.1478	$77.15	$77.15	$77.10
Purchase #4	$67.26	4.706%	$70.4253	$70.43	$70.45	$70.40
Purchase #5	$179.77	3.775%	$186.5563	$186.56	$186.55	$186.60
Purchase #6	$70.60	11.600%	$78.7896	$78.79	$78.80	$78.80
Purchase #7	$225.46	5.674%	$238.2526	$238.25	$238.25	$238.30
7 purchase totals =	$1,001.72		$1,075.9433	$1,075.95	$1,075.95	$1,076.00