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	$182.44	12.759%	$205.7175	$205.72	$205.70	$205.70
Purchase #2	$132.91	8.233%	$143.8525	$143.85	$143.85	$143.90
Purchase #3	$174.86	12.393%	$196.5304	$196.53	$196.55	$196.50
Purchase #4	$194.81	4.538%	$203.6505	$203.65	$203.65	$203.70
Purchase #5	$110.62	4.773%	$115.8999	$115.90	$115.90	$115.90
Purchase #6	$127.77	10.799%	$141.5679	$141.57	$141.55	$141.60
Purchase #7	$147.74	11.246%	$164.3548	$164.35	$164.35	$164.40
7 purchase totals =	$1,071.15		$1,171.5735	$1,171.57	$1,171.55	$1,171.70