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	$45.63	13.455%	$51.7695	$51.77	$51.75	$51.80
Purchase #2	$78.71	3.557%	$81.5097	$81.51	$81.50	$81.50
Purchase #3	$94.63	8.381%	$102.5609	$102.56	$102.55	$102.60
Purchase #4	$157.51	3.412%	$162.8842	$162.88	$162.90	$162.90
Purchase #5	$46.76	6.436%	$49.7695	$49.77	$49.75	$49.80
Purchase #6	$127.83	11.643%	$142.7132	$142.71	$142.70	$142.70
Purchase #7	$37.48	10.119%	$41.2726	$41.27	$41.25	$41.30
7 purchase totals =	$588.55		$632.4796	$632.47	$632.40	$632.60