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	$240.35	11.176%	$267.2115	$267.21	$267.20	$267.20
Purchase #2	$221.74	7.368%	$238.0778	$238.08	$238.10	$238.10
Purchase #3	$58.94	5.788%	$62.3514	$62.35	$62.35	$62.40
Purchase #4	$59.70	6.304%	$63.4635	$63.46	$63.45	$63.50
Purchase #5	$69.75	12.572%	$78.519	$78.52	$78.50	$78.50
Purchase #6	$225.73	3.613%	$233.8856	$233.89	$233.90	$233.90
Purchase #7	$172.59	7.657%	$185.8052	$185.81	$185.80	$185.80
7 purchase totals =	$1,048.80		$1,129.3140	$1,129.32	$1,129.30	$1,129.40