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	$102.86	10.124%	$113.2735	$113.27	$113.25	$113.30
Purchase #2	$216.33	11.586%	$241.394	$241.39	$241.40	$241.40
Purchase #3	$12.57	9.716%	$13.7913	$13.79	$13.80	$13.80
Purchase #4	$179.97	11.627%	$200.8951	$200.90	$200.90	$200.90
Purchase #5	$194.59	7.220%	$208.6394	$208.64	$208.65	$208.60
Purchase #6	$89.45	3.538%	$92.6147	$92.61	$92.60	$92.60
Purchase #7	$157.56	13.783%	$179.2765	$179.28	$179.30	$179.30
7 purchase totals =	$953.33		$1,049.8845	$1,049.88	$1,049.90	$1,049.90