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	$29.61	7.616%	$31.8651	$31.87	$31.85	$31.90
Purchase #2	$247.63	3.629%	$256.6165	$256.62	$256.60	$256.60
Purchase #3	$52.39	3.658%	$54.3064	$54.31	$54.30	$54.30
Purchase #4	$203.47	9.412%	$222.6206	$222.62	$222.60	$222.60
Purchase #5	$151.58	7.475%	$162.9106	$162.91	$162.90	$162.90
Purchase #6	$179.25	9.706%	$196.648	$196.65	$196.65	$196.60
Purchase #7	$73.40	3.540%	$75.9984	$76.00	$76.00	$76.00
7 purchase totals =	$937.33		$1,000.9656	$1,000.98	$1,000.90	$1,000.90