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	$117.25	12.140%	$131.4842	$131.48	$131.50	$131.50
Purchase #2	$200.50	8.386%	$217.3139	$217.31	$217.30	$217.30
Purchase #3	$72.91	4.116%	$75.911	$75.91	$75.90	$75.90
Purchase #4	$60.98	10.534%	$67.4036	$67.40	$67.40	$67.40
Purchase #5	$170.70	4.451%	$178.2979	$178.30	$178.30	$178.30
Purchase #6	$140.27	11.429%	$156.3015	$156.30	$156.30	$156.30
Purchase #7	$65.92	11.103%	$73.2391	$73.24	$73.25	$73.20
7 purchase totals =	$828.53		$899.9512	$899.94	$899.95	$899.90