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	$190.52	3.264%	$196.7386	$196.74	$196.75	$196.70
Purchase #2	$25.61	5.768%	$27.0872	$27.09	$27.10	$27.10
Purchase #3	$132.46	3.454%	$137.0352	$137.04	$137.05	$137.00
Purchase #4	$193.98	7.838%	$209.1842	$209.18	$209.20	$209.20
Purchase #5	$217.56	9.812%	$238.907	$238.91	$238.90	$238.90
Purchase #6	$144.70	5.379%	$152.4834	$152.48	$152.50	$152.50
Purchase #7	$209.59	7.785%	$225.9066	$225.91	$225.90	$225.90
7 purchase totals =	$1,114.42		$1,187.3422	$1,187.35	$1,187.40	$1,187.30