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	$99.85	13.739%	$113.5684	$113.57	$113.55	$113.60
Purchase #2	$120.41	6.218%	$127.8971	$127.90	$127.90	$127.90
Purchase #3	$182.62	5.605%	$192.8559	$192.86	$192.85	$192.90
Purchase #4	$163.80	11.421%	$182.5076	$182.51	$182.50	$182.50
Purchase #5	$71.88	6.416%	$76.4918	$76.49	$76.50	$76.50
Purchase #6	$243.28	3.131%	$250.8971	$250.90	$250.90	$250.90
Purchase #7	$200.38	8.673%	$217.759	$217.76	$217.75	$217.80
7 purchase totals =	$1,082.22		$1,161.9769	$1,161.99	$1,161.95	$1,162.10