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	$151.67	13.179%	$171.6586	$171.66	$171.65	$171.70
Purchase #2	$67.88	7.156%	$72.7375	$72.74	$72.75	$72.70
Purchase #3	$118.63	3.634%	$122.941	$122.94	$122.95	$122.90
Purchase #4	$82.51	4.658%	$86.3533	$86.35	$86.35	$86.40
Purchase #5	$71.72	12.175%	$80.4519	$80.45	$80.45	$80.50
Purchase #6	$62.94	7.241%	$67.4975	$67.50	$67.50	$67.50
Purchase #7	$189.85	9.622%	$208.1174	$208.12	$208.10	$208.10
7 purchase totals =	$745.20		$809.7572	$809.76	$809.75	$809.80