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	$166.98	4.444%	$174.4006	$174.40	$174.40	$174.40
Purchase #2	$92.48	10.562%	$102.2477	$102.25	$102.25	$102.20
Purchase #3	$233.60	11.296%	$259.9875	$259.99	$260.00	$260.00
Purchase #4	$78.67	5.747%	$83.1912	$83.19	$83.20	$83.20
Purchase #5	$72.79	10.766%	$80.6266	$80.63	$80.65	$80.60
Purchase #6	$191.95	11.681%	$214.3717	$214.37	$214.35	$214.40
Purchase #7	$178.25	10.281%	$196.5759	$196.58	$196.60	$196.60
7 purchase totals =	$1,014.72		$1,111.4012	$1,111.41	$1,111.45	$1,111.40