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	$212.43	3.325%	$219.4933	$219.49	$219.50	$219.50
Purchase #2	$134.29	9.523%	$147.0784	$147.08	$147.10	$147.10
Purchase #3	$100.30	5.162%	$105.4775	$105.48	$105.50	$105.50
Purchase #4	$35.48	3.531%	$36.7328	$36.73	$36.75	$36.70
Purchase #5	$38.52	10.681%	$42.6343	$42.63	$42.65	$42.60
Purchase #6	$89.75	12.329%	$100.8153	$100.82	$100.80	$100.80
Purchase #7	$107.74	3.275%	$111.2685	$111.27	$111.25	$111.30
7 purchase totals =	$718.51		$763.5001	$763.50	$763.55	$763.50