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	$55.99	6.354%	$59.5476	$59.55	$59.55	$59.50
Purchase #2	$12.76	11.215%	$14.191	$14.19	$14.20	$14.20
Purchase #3	$187.76	6.765%	$200.462	$200.46	$200.45	$200.50
Purchase #4	$142.32	5.761%	$150.5191	$150.52	$150.50	$150.50
Purchase #5	$140.97	7.838%	$152.0192	$152.02	$152.00	$152.00
Purchase #6	$27.59	6.419%	$29.361	$29.36	$29.35	$29.40
Purchase #7	$64.96	8.741%	$70.6382	$70.64	$70.65	$70.60
7 purchase totals =	$632.35		$676.7381	$676.74	$676.70	$676.70