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	$154.60	4.184%	$161.0685	$161.07	$161.05	$161.10
Purchase #2	$249.37	10.114%	$274.5913	$274.59	$274.60	$274.60
Purchase #3	$50.67	8.802%	$55.13	$55.13	$55.15	$55.10
Purchase #4	$38.83	5.506%	$40.968	$40.97	$40.95	$41.00
Purchase #5	$67.66	12.749%	$76.286	$76.29	$76.30	$76.30
Purchase #6	$172.34	3.815%	$178.9148	$178.91	$178.90	$178.90
Purchase #7	$200.31	11.524%	$223.3937	$223.39	$223.40	$223.40
7 purchase totals =	$933.78		$1,010.3523	$1,010.35	$1,010.35	$1,010.40