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	$222.78	9.684%	$244.354	$244.35	$244.35	$244.40
Purchase #2	$87.73	9.271%	$95.8634	$95.86	$95.85	$95.90
Purchase #3	$189.65	3.804%	$196.8643	$196.86	$196.85	$196.90
Purchase #4	$98.82	9.179%	$107.8907	$107.89	$107.90	$107.90
Purchase #5	$222.88	11.686%	$248.9258	$248.93	$248.95	$248.90
Purchase #6	$77.98	6.249%	$82.853	$82.85	$82.85	$82.90
Purchase #7	$188.77	7.751%	$203.4016	$203.40	$203.40	$203.40
7 purchase totals =	$1,088.61		$1,180.1528	$1,180.14	$1,180.15	$1,180.30