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	$242.26	3.132%	$249.8476	$249.85	$249.85	$249.80
Purchase #2	$201.69	12.188%	$226.272	$226.27	$226.25	$226.30
Purchase #3	$229.58	6.632%	$244.8057	$244.81	$244.80	$244.80
Purchase #4	$177.89	10.276%	$196.17	$196.17	$196.15	$196.20
Purchase #5	$142.69	6.394%	$151.8136	$151.81	$151.80	$151.80
Purchase #6	$197.59	3.181%	$203.8753	$203.88	$203.90	$203.90
Purchase #7	$72.49	8.310%	$78.5139	$78.51	$78.50	$78.50
7 purchase totals =	$1,264.19		$1,351.2981	$1,351.30	$1,351.25	$1,351.30