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	$56.38	13.422%	$63.9473	$63.95	$63.95	$63.90
Purchase #2	$39.33	3.590%	$40.7419	$40.74	$40.75	$40.70
Purchase #3	$205.86	13.453%	$233.5543	$233.55	$233.55	$233.60
Purchase #4	$38.32	10.841%	$42.4743	$42.47	$42.45	$42.50
Purchase #5	$182.98	3.540%	$189.4575	$189.46	$189.45	$189.50
Purchase #6	$247.32	12.704%	$278.7395	$278.74	$278.75	$278.70
Purchase #7	$207.73	6.238%	$220.6882	$220.69	$220.70	$220.70
7 purchase totals =	$977.92		$1,069.6030	$1,069.60	$1,069.60	$1,069.60