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	$69.98	5.307%	$73.6938	$73.69	$73.70	$73.70
Purchase #2	$109.43	6.427%	$116.4631	$116.46	$116.45	$116.50
Purchase #3	$145.61	9.738%	$159.7895	$159.79	$159.80	$159.80
Purchase #4	$38.90	10.818%	$43.1082	$43.11	$43.10	$43.10
Purchase #5	$127.69	11.782%	$142.7344	$142.73	$142.75	$142.70
Purchase #6	$123.29	7.796%	$132.9017	$132.90	$132.90	$132.90
Purchase #7	$105.48	13.563%	$119.7863	$119.79	$119.80	$119.80
7 purchase totals =	$720.38		$788.4770	$788.47	$788.50	$788.50