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	$13.49	6.293%	$14.3389	$14.34	$14.35	$14.30
Purchase #2	$127.67	10.806%	$141.466	$141.47	$141.45	$141.50
Purchase #3	$30.89	3.214%	$31.8828	$31.88	$31.90	$31.90
Purchase #4	$90.49	6.588%	$96.4515	$96.45	$96.45	$96.50
Purchase #5	$103.75	7.630%	$111.6661	$111.67	$111.65	$111.70
Purchase #6	$134.91	10.223%	$148.7018	$148.70	$148.70	$148.70
Purchase #7	$42.66	10.530%	$47.1521	$47.15	$47.15	$47.20
7 purchase totals =	$543.86		$591.6592	$591.66	$591.65	$591.80