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	$160.86	9.638%	$176.3637	$176.36	$176.35	$176.40
Purchase #2	$174.44	8.759%	$189.7192	$189.72	$189.70	$189.70
Purchase #3	$25.58	6.507%	$27.2445	$27.24	$27.25	$27.20
Purchase #4	$35.60	10.637%	$39.3868	$39.39	$39.40	$39.40
Purchase #5	$99.34	6.652%	$105.9481	$105.95	$105.95	$105.90
Purchase #6	$65.59	3.287%	$67.7459	$67.75	$67.75	$67.70
Purchase #7	$131.35	11.809%	$146.8611	$146.86	$146.85	$146.90
7 purchase totals =	$692.76		$753.2693	$753.27	$753.25	$753.20