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	$120.64	11.675%	$134.7247	$134.72	$134.70	$134.70
Purchase #2	$24.93	8.318%	$27.0037	$27.00	$27.00	$27.00
Purchase #3	$176.28	3.521%	$182.4868	$182.49	$182.50	$182.50
Purchase #4	$236.56	11.419%	$263.5728	$263.57	$263.55	$263.60
Purchase #5	$94.54	9.251%	$103.2859	$103.29	$103.30	$103.30
Purchase #6	$131.39	4.283%	$137.0174	$137.02	$137.00	$137.00
Purchase #7	$177.96	10.527%	$196.6938	$196.69	$196.70	$196.70
7 purchase totals =	$962.30		$1,044.7851	$1,044.78	$1,044.75	$1,044.80