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	$115.64	11.392%	$128.8137	$128.81	$128.80	$128.80
Purchase #2	$159.29	8.574%	$172.9475	$172.95	$172.95	$172.90
Purchase #3	$186.74	5.372%	$196.7717	$196.77	$196.75	$196.80
Purchase #4	$161.29	3.366%	$166.719	$166.72	$166.70	$166.70
Purchase #5	$150.59	5.644%	$159.0893	$159.09	$159.10	$159.10
Purchase #6	$164.32	13.589%	$186.6494	$186.65	$186.65	$186.60
Purchase #7	$35.63	12.646%	$40.1358	$40.14	$40.15	$40.10
7 purchase totals =	$973.50		$1,051.1264	$1,051.13	$1,051.10	$1,051.00